usefull link

useful link to preppair us for instances

http://www.tankspot.com/

# Boss mods for all raid bosses
# Colored raid warnings (players will be colored according to their class) with icons - so you will know what's going on without even reading the message

http://wow.curse.com/downloads/wow-addons/details/deadly-boss-mods.aspx

Omen is a threat meter. Basically, enemies in WoW decide who to attack by deciding who is the most threatening based on the abilities you use. What Omen does is provide accurate values of your group's relative threat level on individual enemies, so that you can see when you're in danger of pulling aggro (or, if you're next on the snack list if your tank bites it). This info is usually only critical in raids, where only tanks can survive aggro, but it's useful for any multi-player situation.

http://wow.curse.com/downloads/wow-addons/details/omen-threat-meter.aspx