Difficult to give any advice when you don't list which 12" PB you have and how much RAM, how much empty HD space, etc.
Main thing to do is simply to buy a small desk fan, elevate the rear of the 12" using gum erasers or whatever, and blow air across yourself and the PB while gaming (or anything processor intensive...) It'll lower your temps drastically.
Summer room temps are also a contributing factor.