Well since ive got all six players i'd better get to the rules, so:
Im allowing:
All core rulebooks
PH II
Planar Handbook and Manual of the Planes
all Complete Books
all Races of Books (including Race of the Dragon, but not Races of Eberron)
The Spell Compendium (all spells should come from the above books, any exceptions - just show me the spell and I'll let you know)
Feats/Skills from the Panewalker.com site (anything else, just ask me and ill let you know)
Tome of Magic (i like all classes in that book though i doubt anyone will use them)
Magic of Incarnum and Expanded Psionics Handbook (i wont be using anything from those books but if anyone wants to use feats/classes etc from there, feel free to)
and Fiendish Codex I: Hordes of the Abyss
Ability Scores: 32 point buy, should make pretty good characters with that
HP: 1/2+1 (1st level is max, as usual)
Starting Gold: 9000, no item can be worth more than 4,500 (magical items from the abov books only, no exceptions).
List your characters' languages, alignment and Faction (and religion, if any). These are all quite important
And, as Thanee pointed out, keep in mind that outsiders are not humanoids, so many spells do affect them differently (that what things like charm monster etc are for)
And finally: anyone who is a faction member may have an extra feat chosen from the faction feats at the Planewalker.com site. The character should be a member-in-good-standing of the fation if he/she is to have such a feat. i leave it up to you whether or not to take the feat (all prerequisited do apply)
Rules:
all standard PH rules, with the addition of Defence Bonus and Armour as DR. no more no less