Quite possibly the most useful addon for anyone interested in running instances, the Deadly Boss Mod (DBM for short) will put up alerts when things are about to happen during an instance and will help to keep you alive. This isn't required, but it does make keeping your Addons in order much easier. First off, I think that anyone who plays Warcraft should download a copy of the Curse Client and have an account with Curse so you can keep track of your Addons better.