Ok so after getting all done and you feel you are geared (no less than 70lvl rares)! and motivated! got all heroic keys! and Applepie! then you need to realise the hardest downside of raiding is not casual. Average Raid with great group eats around 100g+ depending on wipes. So. Do daily quests and you should be fine.

All members of the raid group need :

Patience.
Understanding.
No Elitist or Noob behavior.
Following Orders to the letter.
Knowledge of the Instance at least from Internet.
Now material things :

-food, water (a lot)
-ammo and pet food (if hunter)
-reagents for spells
-potions < !

A great list of potions needed you can find here :
http://wow.gameamp.com/wow/viewRaidPrep

Best way to make potions is to have alchemy char or grind a lot of gold.