I recommend the Goetia and works in Enochiana for purposes of study. The former deals with demons and their summoning/controlling and the latter deals with angels and their prophesies (along with their language). An interesting site that deals with the Goetia in rather simplified (and perhaps incomplete) terms is:
http://www.disciplina.org/members/paradigm.htm
Digital books on ceremonial magick, most of which deals with demons can be found here:
http://chaosmatrix.org/library/books.php
If you want a slightly different portrayal of the demons featured in the Goetia, then you could look at:
http://www.angelfire.com/empire/serpentis666/, though that site is frowned upon by most Satanists. You can also look into the demonolatrist view of things (as they worship demons almost exclusively) and look at their rituals (which can sometimes be quite painful and involving tattoos and branding).
Other 'lists' of demons:
http://overman666.tripod.com/c.html, though it explores the different ways these demons are classified through various texts:
http://overman666.tripod.com/list.html.
http://overman666.tripod.com/p.html. Also:
http://overman666.tripod.com/Diction.html
In my experience, there are plenty of creatures of trickery, specifically demons who have been the scapegoats of poor luck and poor personality traits for centuries. They tend to be rather dishonest and wiley, and feed off of desperation. If you happen to conjure one of these demons without proper preperation then chances are you could fall into one of his/her traps as they are quite clever. They can be extremely powerful to work with but they are...rather lazy. They always try to talk their way out of things or try to run away without ever doing the work they were supposed to do. If allowed, the magician might be bound to the demon through some sort of pact and it might turn out that the magician is the one doing all of the work and suffering while the demon just slacks off. Demons also manifest desires, and they can easily cause imbalance in a person's life if conjured irresponsibly.
Considering most 'safe' means of conjuring demons involves quite a while to set up, the magician must first be certain of his goals. He must have done his research. And he must cast his demands upon the demon with conviction. If a demon tries to say to you: give me more time, you've got to have the power to say: no! right now! If a demon says I can't do that, then you've got to have the heart to bitchslap him around and tell him that you've done your research and that you know full well that he can.
Demons are tricky business and it's easy to fall into their tricks if you're not careful. Certainly don't try to make too good friends with them without suspecting that they're feeding you lies.