I'm not a keyboard turner -- my steady diet of FPS games growing up made sure of that. And while I do occasionally point-and-click abilities, for the most part, I do use hotkeys. But, just like Tank Like a Girl, there is one control-scheme sin that I'm definitely guilty of: I am definitely a Tab-targeter. I guess the issue is that sometimes you do have to use Tab to choose your different targets -- sometimes, you can't quite click on the thing you need to target, so instead you hit Tab to flip through all the available targets until you get to the one you need. But that's a no-no. Flipping through the targets takes more time than you should (if you happen to miss your target, you need to flip through all of them yet again), and, as I know from personal experience, Tab targeting often ends you up on the wrong target. Not that CC is so much of an issue anymore, but let me tell you: the first time you happen to pull that one dragon your group has cast sleep on, it'll be embarassing.
So how to get it right? TLaG suggests this post from TankingTips, which hints at using the mouse instead of the keyboard to target (you can choose friendly targets easier that way), but doesn't offer any real suggestions of how to make the switch. Moving the camera back is one, getting your positioning right is probably another. And learning to use focus and macro targets is probably the best tip you can have: anything that's more specific or direct than either Tab or click targeting is probably better. Addons like Promixo will help in the Arenas as well.
No one's perfect, and no one way to do things is perfect either -- depending on your situation, Tab targeting might be better. But it's important to have as many tools as possible, so if you, like me, find yourself depending on the Tab key more often than not, it might be time to mix up your toolbag a bit.