Suggestions on how to properly split test?

I have been running my PC campaigns on adcenter for about a year now and have really just set up some bids and called it a day. I realize I should start testing what is working and what isn't, but want to do this in the most efficient way.

I was wondering if anyone could point me to some good reads on spit testing ppc campaigns, and maybe bidding strategies, for adcenter only, because I don't use adwords (way too expensive and far fewer conversions compared to adcenter, in my experience). I have been searching google and there really isn't much info on adcenter, it's all about adwords.