I'm looking for concrete theological beliefs and practices on where they differ. Christians say that Mormons aren't Christian and yet Mormons call themselves Christian. So it can be quite hard to tell for a everyday person who is who and what is what.
The "Evangelical" movement spreads across an incredibly wide range of beliefs, so it will be hard to nail this down, but a few things come to mind that ought to have broad acceptance and make at least some form of answer possible. For convenience in the rest of this answer, please treat the word "Evangelical" merely as broadly representing "Most Evangelicals".
The root question here, though, is whether or not Mormons are themselves even Christian. To understand this, you need to look at it from both sides. In a broad sense, one is a Christian when one acknowledges the person of Christ as their creator and Lord. Everything else — all the denomitions, splits, and arguments — is just details.
With that in mind, the Non-mormon Christian perspective is that Mormons have been lead astray, and have allowed the teachings of Joseph Smith and his successors to supersede and in many cases replace those of Christ... and so they no longer follow Christ supremely, but (perhaps unwittingly) follow the teachings of Joseph Smith instead. Moreover, since Mormons refuse to grant Jesus full unity with God the Father, but hold him separate from God the Father, it is offensive to mainline Christians to watch Mormons hold up the teachings of Joseph Smith to the level of Christ, yet still use the name of Christ to describe themselves.
The Mormon perspective is that Joseph Smith's teachings are Christ's teachings, that Joseph Smith was merely His mouthpiece. They hold both the Old and New Testaments to be scripture (just not all scripture), and so to be considered "not Christian" is offensive to Mormons, because they still believe that Christ died for their sins, just as "regluar" Christians do.
Christians believe the Bible and the traditional understanding of what the Bible teaches, as summarized through the centuries in the various creeds (Nicene Creed, Apostles' Creed, Westminster Confession, etc). All Christian denominations, both Catholic and Protestant, are united in the following beliefs taken directly from Biblical teachings:
Mormonism differs from Christianity in that Joseph Smith, Brigham Young (and others) taught that there have been more recent gospels: the Book of Mormon, Doctrine & Convenants, Pearl of Great Price -- as well as all sermons preached by Smith and Young as recorded in the Journal of Discourses.
Further, the Mormon church teaches that the Bible is a lesser source, in that it has been "corrupted" and is essentially not the same as what was first written. (This game, under a different name, "Post Office", is often used as an example of how/why that happened.) Therefore, Mormons say, it is more important to read/believe the latter teachings. However, Christians point to examples from archaeology, such as the 1947 Dead Sea scrolls discovery, in which most books of the Old Testament were discovered, dating back 100 years before the birth of Jesus. The book of Isaiah, for example, shows only 13 characters in question, none of which change the meaning of any phrase. On the other hand, the Book of Mormon (to compare apples with apples) even changes the identity of God in one of it's 3,900+ changes since it was first published in 1830. (Compare 1 Nephi 11:18 and 1 Nephi 11:21 with their originals in 1830. Knowing Mormon theology, you will know that "God" and the "Son of God" are Elohim and Jehovah, respectively. This is a significant, theology-altering, change.)
Over and above the Bible's teachings, and sometimes in conflict with the Bible's teachings, the Mormon leaders taught that:
There are a vast number of other differences between the teachings of Christianity and Mormonism. You may wish to investigate the following areas: polygamy (many wives), polytheism (many gods), archaeology, scripture, the nature of God, the Trinity, the history of Christianity.
Most Christians who have investigated the claims and teachings of Mormonism firmly state that there are virtually NO common essential beliefs between Christianity and Mormonism. This matter is confusing to many people because Mormon teachings use the same names/words as Christian sources, but with completely different meanings. For example, the Mormon Jesus is not at all like the Christian Jesus, although the Mormon Jesus is said to BE the Christian Jesus. However, if you compare their origins, what they claimed about themselves, and their position after death, you will see little resemblance. They are two totally different beings.
Simply put Evangelicals differ over at least three primary things:
1. The Nature of Jesus
Evangelicals believe Jesus to be God - of one being with Father, God from God, Light from Light, true God from true God, etc... Mormons do not. Mormons believe Jesus to be divine, but a separate person from the Father. Evangelicals tend to subscribe to the historic creeds of the church - Nicene, Apostles, etc... - and are almost invariably Trinitarian. (I cannot say that I have ever run across a non-Trinitarian Evangelical, but as it is a movement and not a denomination, there are always exceptions).
Note: In the comments, there was a notion that the creeds only adhered to the "Catholic" church. Insofar as "catholic" is understood as "universal" or "what most people think of when they think of 'mainstream' Christianity, that is accurate. If that were taken to mean the 'Roman Catholic Church,' that would be precise, but inaccurate, in that most Protestants and Orthodox also subscribe to the Creeds and to the Trinitarian formulations thereof.
2. The nature of the "Bible"
3. The nature of soteriology
Evangelicals, by and large, believe salvation to be solely the gift of God. We believe that all who are saved entire into eternal relationship with God. Mormons believe that people are rewarded according to the nature of the covenant they believed.
Q: practices on where they differ? These practices are different to Evangelical groups.
All LDS adults are also Priests, and the responsibility for their neighbors is a covenantal promise. Everyone in the local Church has a Priest assigned to them and he visits the home every month to see if anything is needed, and reports back to the Bishop.
LDS live a life of Christ, as far as it is possible in this day and age. They are monitored by the brethren and warned if they stray from God's Will as it is defined by Scripture and by revelations of the Prophets.
None of the clergy is paid. As in the early Church, each person must support themselves with a job outside the Church.
The Church has a central authority. Everyone believes the same theology. There is no disagreement in the Church.