revision: working on bad guys

My next big project (after I get home from school next week) will be revising my novel. Specifically, I have to work on my bad guys. I've been told they're too warm and fuzzy, not realistic, etc. So, obviously, I've got some work to do! I must admit I have trouble writing evil. It seems so melodramatic--maybe that's because I'm not doing it right! :)

Awesome Fantasy author Carol Berg discusses Writing Evil today over at her agent Lucienne Diver's blog. Among other things Carol says Something that bothers me ...is our tendency to toss people ...into binary bins... as we mature, we know life is just not that simple...

Ah ha! Maybe I should quit thinking of them as "bad guys" and instead focus on them as guys who have different and opposing goals to the protagonist. Hhm... I may be on to something here.

How do you revise? Do you pick a particular area and focus on it (like I'm trying to do)?
Does anyone have any tips for writing antagonists?