I love papering (sad)!!!
My tips:
As above about not papering round corners.
Plumbob (dangly weight thing on string) to make sure you are getting the pieces straight.
Paste a piece and let the paste soak in for a couple of minutes (don't worry about how wet it looks on the other side) this helps prevent wrinkles and bubbles.
Pencil and Tape measure for the obvious.
Seam Roller - amazing how useful they are. line up your pattern to last peice, and use seam roller to get the edge right. Once you have this correctly, the rest of the paper follows pretty easily. Use this also for pushing paper into skirting and cornice edge.
Use scissors for cutting sections of paper, but I use a very sharp craft knife for cutting in. Must keep changing the blade to keep your edges immaculate.
Use soft cloth for putting paper onto the wall, rubbing over from the centre outward to get rid of bubbles, obviously from top to bottom.
Clean of excess paste with a damp sponge from paintwork.
Papering is fun! Don't be scared of making a mistake, you become very resourceful at rectifying them. And these are just my way of doing it, you will find your own!
So, thats it, but my main one is don't be scared of it.
Good Luck!