One way to avoid the rash is to titrate slowly up on the med. This is especially important when it comes to Lamictal because the rash can be quite serious. I was on Lamictal and titrated very slowly and had no problems. The only problem was that Lamictal caused me to have Myoclonic jerks and I also had weight gain on it so my Dr took me off it. Many people have success on it though.
I have been on Lamictal for about 2 years now. I was titrated very slowly over many weeks up to my current dose of 400mg daily. I have heard about the rash with Depakote. I did not experience any rash thank goodness. The only drug I think I have not been on is Depakote. My most prominent side effects with Lamictal were nausea, motion-sickness, and weight loss. It probably took me the good part of a year before I got over most of the side effects. Although it hasn't been the most effective drug that I've taken, it's not the worst either and at least I don't have to get blood tests to check my liver like I did when I took Dilantin.
AmandaJane is right about the trial and error stuff. It's amazing how similar we all are - in that most of us have gone thru lots of trial and error with our meds. There really isn't any magic formula.
Hope you have some luck with your medications... I'll be thinking of you .