I watched the entire series of The Exorcist movie and I enjoyed it. However, I am curious if this movie is representing the reality about demons and how they are driven out by Catholic priests.
Not all Catholic priests are specially trained in the sort of exorcism depicted in the film (although a particular form of exorcism is contained in the rite of baptism). Major and specific exorcism is a specialist ministry for which some are more suited than others.
Sacerdos, seu quivis alius legitimus Ecclesiae minister, vexatos a daemone exorcizaturus, ea qua par est pietate, prudentiae, ac vitae integritate praeditus esse decet.
A priest or other legitimate minister of the Church chosen to exorcize a demon should be endowed with piety, prudence and integrity of life.
While all priests are expected to be “endowed with piety, prudence and integrity of life”, only some will exhibit the levels which make them suitable to be “chosen to exorcise a demon”.
There is a manual, De Exorcismis et supplicationibus quibusdam, (Of exorcisms and certain supplications) published in 1614 and revised in 1999. The official edition is in Latin, but at least one unofficial English translation exists. The new edition acknowledges the possibility of mental illness which should not be confused with demon possession, but it does maintain that evil exists, and
The Devil and other demons can not only afflict persons (by temptation and vexation), but also places and objects, and can cause various forms of opposition and persecution of the Church.
A Guardian report on the new manual said that "All Roman Catholic dioceses have an exorcist — a priest specially appointed to the post by his bishop. But the degree to which exorcists are used is said to vary enormously, and Church officials say that in some parts of the world they are scarcely employed at all."
Along with the great answer by Andrew Leach, I would like to point out that a priest or a bishop are valid ministers to perform a exorcisms.
Are all Catholic priests trained to perform exorcism?
Even though all priest can perform an exorcism, there seems to exist a special training for it.src
Is there any guidelines for casting out the demons or evil spirits?
Apart from the prayers Andrew Leach has pointed out, the canon law mandates that a priest should get the permission of his bishop before performing an exorcism.Can. 1172 Usually permission to perform an exorcism is given only if it can be proved beyond any reasonable doubt that the condition of the person who is possessed cannot be explained physiologically. Like for example fluency in foreign languages unknown to the person, super human strength etc.,
Other than this there are some 21 instructions present in the Roman Ritual. These are guidelines on what to do, where to do and how to do it.
Do they cast out demons very often?
This is really difficult to tell because such statistics are not released publicily. But Father Gabriele Amorth the chief exorcist for the Diocese of Rome, says he's done more than 160,000 exorcisms.src
