This isnt a bad guide for someone thats never done it before - its a bit wordy but pretty accurate. The site itself is quite handy too.
http://www.diydoctor.org.uk/projects/wallpapering.htm
My personal tip would be to use a caulking tool instead of a brush for smoothing the paper out - use it at a very low angle and gently - its much better for getting bubbles out of the paper
Dont oversoak papers - nothing worse than when it falls apart!
Always follow the instructions on the roll and always make sure when getting multiple rolls that you get the same batch number and the same pattern number (if it has a pattern number) otherwise the rolls wont match
Start from a window and work your way round, but if you have a fireplace start from there (ideally with your first strip exactly in the middle of the chimney breast)
Size the walls first if the walls are dry or porous and dont be afraid of putting loads of paste on the walls!
Use plenty of paste on the paper and double check the edges! Its easy to miss the edges.
When buying paper, its 'normally' four strips to one roll (although could be more when matching a pattern. Treat a window or door as a ordinary wall to make sure you buy enough as you will have offcuts.
If you are using lining paper, 1000g paper is good to use (you can also get 800 and 1200g) as it is thick but not so thick that its hard to hang. Lining paper also comes in doubles or quads, which are just waht they say. Double size rolls or rolls that are 4 times as long as a normal roll
If you are new to it, paste and hang one strip at a time.
Cant think of anything else for now!