At first I was thinking the only requirement to be canonized was to be killed for your faith. Is this accurate? How is someone deemed a Saint as opposed to a martyr in Catholicism?
The process is called canonization. Wikipedia's article on canonization describes the process. Martyrdom is not a requirement for sainthood, although being martyred does suggest that a person may very well be a saint (think John 15:13, Greater love than this no man hath, that a man lay down his life for his friends.). Mother Theresa is a great example of a non-martyred saint, canonized because of the great witness of her life of love and compassion for the poor in India.
In summary, a person is recognized by a bishop or other church person with sufficient authority as a possible candidate for sainthood, and an investigation is started. The Congregation for the Causes of the Saints investigates this information, and eventually may make a recommendation that the pope make a declaration that the Servant of God is 'heroic in virtue'. At this point, the potential saint becomes known as 'Venerable', meaning that Catholic may encourage veneration of this person, such as prayers for intercession, but the church has made no official statement on whether or not it is believed that the person is in Heaven.
The next step is where martyrdom matters. If the Pope makes a declaration of martyrdom, then the martyr can be canonized, as the Catholic church teaches that all martyrs go to Heaven, and being in Heaven is the definition of a 'capital-S' Saint.
If the person was not a martyr, then the person is considered a 'confessor', a person who bore witness to Christ (confessed Christ) through the way they lived their life. A miracle achieved through the intercession of the venerable must be documented before a confessor can be beatified, and can be called "Blessed" (but still not a saint yet!). There are strict guidelines in evaluating miracles to determine their authenticity. For a confessor to be canonized, and declared a saint, two miracles are required.
Note that this is a summary, and I am leaving details out - such as requirements for time to pass before canonization. Also, I am not an expert in Catholic canon law; while the general information is accurate, I could have details wrong. If you want to hear from an expert, you could go to Catholic Forum's Ask an Apologist subforum and send in your question.
Since wikipedia loads of good info, I'll just answer the question.
How is someone deemed a saint (in 2011)?
The pope canonizes a dead person who has lived a life of heroic virtue and has performed a posthumous miracle in addition to the miracle required for beatification.
What about martyrdom?
Martyrdom circumvents the normal requirement of a posthumous miracle for beatification, but it not instant qualification for sainthood.
Other saintly terminology:
Someone who has been beatified is referred to as Blessed, someone who is canonized is referred to as Saint. You may also see Venerable and Servant of God, these are mile markers on the path to sainthood.
There's a path to follow.
"Servant of God"
The local bishop recognizes that someone holy has died and starts gathering evidence that they were holy. When they have enough evidence, they give the evidence to the Roman Curia.
"Declaration 'Non Cultus'"
At some point, they dig up the body and gathers a few relics.
"Venerable/Heroic in Virtue"
When there's enough evidence that they were actually holy, the Pope (at the recommendation of the Roman Curia) declares them as Venerable.
The person, at this point, is declared that they are actually, truly in heaven "looking at God". If they were a martyr, the Pope gives it the rubber stamp. Otherwise, there has to be a proven miracle tied to the person. This is called the Beatific Vision.
To become a saint, there has to be two proven miracles. Once there are two miracles, the Pope may proclaim that person a saint.
So, to answer your question, martyrdom is not a requirement for sainthood. Nor is it a guarantee. You have to have associated miracles to achieve Sainthood.
The treatment of martyrs as saints has varied considerably over the years. It started as an almost spontaneous, bottom-up approach, spurred by initial persecutions under the Roman Empire, where martyrs and their relics were "spontaneously" venerated (i.e. treated as saints, in modern terminology) by Christians. Later on, as the Church grew in size and complexity, a "process" was required in order to grant sainthood status. Here, miracles were considered an "insurance policy", as it was possible that a martyr had renounced his/her faith in the last minute. This process became more complex and legalistic over time, albeit in recent decades it has simplified a bit, even allowing canonisation of martyrs as saints without need for miracles.
Some historical comments.
First of all, the veneration of saints started off from the veneration of Martyrs, which neither required nor had a canonisation process. As this site about Canon Law states:
The Church’s first “saints” (derived from the Latin word sancti, or “holy ones”) were martyred for their faith during the Christian persecutions. The early Christians quickly began to commemorate annually the dates when the martyrs had died—a practice which soon led to set liturgical calendars, containing feast-days for the various saints. In the first centuries of Christianity, there certainly was no legal process for the canonization of saints; rather, it was obvious to all that if a Christian had been killed because he refused to renounce his belief in Christ, he had undoubtedly entered Heaven after making what was considered the ultimate act of virtue. In short, people knew a saint when they saw one! Thus there was no need for legal procedures, for canon lawyers, or even for miracles—the martyr’s fellow-Christians simply began venerating him as a saint, and that was that.)
Particularly important in this veneration process was the collection of martyrs relics. This entry in the Catholic Encyclopedia about martyrs and persecution in the Roman Empire before Constantine states:
It is easy to understand why those who endured so much for their convictions should have been so greatly venerated by their co-religionists from even the first days of trial in the reign of Nero. The Roman officials usually permitted relatives or friends to gather up the mutilated remains of the martyrs for interment, although in some instances such permission was refused. These relics the Christians regarded as "more valuable than gold or precious stones" (Martyr. Polycarpi, xviii). Some of the more famous martyrs received special honours, as for instance, in Rome, St. Peter and St. Paul, whose "trophies", or tombs, are spoken of at the beginning of the third century by the Roman priest Caius (Eusebius, Church History II.21.7). Numerous crypts and chapels in the Roman catacombs, some of which, like the capella grœca, were constructed in sub-Apostolic times, also bear witness to the early veneration for those champions of freedom of conscience who won, by dying, the greatest victory in the history of the human race. Special commemoration services of the martyrs, at which the holy Sacrifice was offered over their tombs — the origin of the time — honoured custom of consecrating altars by enclosing in them the relics of martyrs — were held on the anniversaries of their death; the famous Fractio Panis fresco of the capella grœca, dating from the early second century, is probably a representation (see s.v. FRACTIO PANIS; SYMBOLS OF EUCHARIST) in miniature, of such a celebration. From the age of Constantine even still greater veneration was accorded the martyrs. Pope Damasus (366-84) had a special love for the martyrs, as we learn from the inscriptions, brought to light by de Rossi, composed by him for their tombs in the Roman catacombs.
Yet, and specially once the Catholic faith was not longer persecuted but promoted by the Roman Empire, and martyrs were not longer numerous, the veneration of "holy people" extended to non-martyrs too. Quoting again from the first link above:
Not every early Christian who led an exemplary life was martyred, however, and so the Church soon began to venerate non-martyrs as well. Local bishops who died of natural causes were among the first to be regarded as “saints” by their congregations, who would have been well aware of their leaders’ personal holiness. Consequently, at a very early point in the history of the Church, we already find some people being commemorated even though they hadn’t been called to make the ultimate sacrifice of their lives for Christ. Eventually the two groups were categorized as “martyrs” and “confessors” (or in the case of female non-martyrs, “widows” and “virgins”).
Later, in the Middle Ages, martyrdom was rare. Similarly the Church was getting bigger, so not all potential saints were to be so popular to many. This is when a "process" was started to develop in order to establish sainthood. And how to do so? Well, miracles were a "proof" that the candidate was already in Heaven! Continuing the quotations:
Nevertheless, at some stage it became common to allege, as part of the “case” in favor of regarding a deceased Christian as a saint, that miraculous cures were taking place as a result of his intercession. Surely (it was argued) this constituted definitive proof that the person must already be in Heaven, and able to intercede with God on our behalf! In this way, the notion gradually developed that miracles are evidence that a deceased person is indeed a saint.
The role of miracles was cemented by Pope Innocent III in 1198 when he stated:
“Two things are required, so that somebody may be considered a saint in the Church Militant, namely works of piety during his life, and miracles after death.” [However] “neither merits without miracles, or miracles without merits fully suffice to present evidence of sanctity… for an angel of Satan can transform himself into an angel of light, and certain persons may do their works in order that they may be seen by men.”
What about martyrs? Given the core importance of miracles in the canonisation process, it was not clear how to treat martyrs. Hence, Pope Urban VIII asked the opinion to a commission of experts. Continuing the quotations:
Eventually they concluded that in cases of clear-cut, undeniable martyrdom, miracles are really not necessary for canonization. In those cases where the person’s death as a martyr is more open to question, however, the occurrence of miracles actually constitutes verification that the potential saint did indeed die as a genuine martyr. After all, it’s theoretically possible that someone who dies a martyr’s death might have reneged on his faith at the last minute—meaning that his supposed “martyr’s death” was actually nothing of the sort! Thus miracles constitute a sort of “insurance policy” even in the cases of martyrs, to make sure that even if their death didn’t really constitute martyrdom, they nevertheless must be in Heaven today, able to intercede before God for us here on earth.
This approach of "insurance policy" continued over the centuries, even until late 20th century. Yet, "today", this is less stringent:
Today, the norm is that one proven miracle is required for beatification, and one for canonization. But the rules currently in force contain a new twist: in the case of a martyr, it is no longer necessary to establish that a miracle has been performed in order to obtain his beatification. Once his martyrdom has been proven, a candidate for Catholic sainthood can be beatified without any miracles at all—simply because he is a martyr. The overall process is still amazingly complicated, tedious, and expensive; but we see here the possible beginnings of a return to the (much simpler!) historical tradition.
In summary, the treatment of martyrs as saints has varied considerably over the years. It started as an almost spontaneous, bottom-up approach, spurred by initial persecutions under the Roman Empire, where martyrs and their relics were "spontaneously" venerated (i.e. treated as saints, in modern terminology) by Christians. Later on, as the Church grew in size and complexity, a "process" was required in order to grant sainthood status. Here, miracles were considered an "insurance policy", as it was possible that a martyr had renounced his/her faith in the last minute. This process became more complex and legalistic over time, albeit in recent decades it has simplified a bit, even allowing canonisation of martyrs as saints without need for miracles.
If you define a martyr as someone who sheds their blood in the name of Christ, the answer is no.
(Pope Eugene IV, Ecumenical Council of Florence)
It [i.e. the Catholic Church] firmly believes, professes and preaches that all those who are outside the catholic church, not only pagans but also Jews or heretics and schismatics, cannot share in eternal life and will go into the everlasting fire which was prepared for the devil and his angels, unless they are joined to the catholic church before the end of their lives; that the unity of the ecclesiastical body is of such importance that only for those who abide in it do the church's sacraments contribute to salvation and do fasts, almsgiving and other works of piety and practices of the Christian militia produce eternal rewards; and that nobody can be saved, no matter how much he has given away in alms and even if he has shed his blood in the name of Christ, unless he has persevered in the bosom and the unity of the catholic church.
Thus, if a formal heretic or schismatic dies for professing Christ, he would (very sadly) go straight to hell unless he is joined to the catholic church before the end of his life. And of course, no one in hell can be a saint.
This may shocking at first, but consider the fact that formal heresy (as opposed to material heresy) is one of the gravest sins, and that anyone who dies in mortal sin goes to hell. (CCC 1861)
Imagine the case of a masturbator living in mortal sin, but who nevertheless is sentenced to death for professing himself to be a Christian. Hopefully, he will repent of his masturbation before the end of his life and God will restore him to the state of grace. But, if he will harden his heart and remain unrepentant even until the bitter end, loving lust more than God, he will go straight to hell.
In the late 1800s, a group of 23 Anglicans and 22 Catholics in Uganda were put to death for professing Christ. Although Pope Paul VI stated that he did not "wish to forget the others who, belonging to the Anglican confession, confronted death in the name of Christ," he only canonized the 22 Catholic martyrs.
Thus, the salvation of the 23 Anglican martyrs remains a mystery. Perhaps they never fully and formally embraced the Anglican heresy, and thus never actually separated themselves from Christ's mystical body. (When someone is baptized as an infant, even in a non-Catholic sect, the person is mystically united to the Catholic Church.) Or maybe they, in the hour of their death, repented of their heresy and were saved, much like the Good Thief.
I see a lot of heresy in these answers.
Remember that ALL martyrs are saints. You don't need any miracles. Read the catechism.
A martyr is washed in his blood and cleansed for all previous sins as he makes a final act of devotion and love for Christ. If dying for the one who died for your sins does not make you an instant saint, nothing does.