Honestly the biggest piece of non-obvious advice is that flash enmity scales with your weapon damage. Tanks are the most gear-dependent of the roles; the better you're geared the easier your healer will have it, freeing them to DPS more if you're as geared as you can be. So more than anyone else, keep your gear up to date, especially your weapon and especially when you'll be on the lower end of the level curve for a dungeon.