A lot of people think of the process as carving out EQ valleys for the kik (or bass) to sit in. I do this to an extent. If your bass is sine wavey and your kik is an 808, you have problems. In that case I would use MaxxBass to add higher harmonics to the bass. If the kik is lower sounding that the bass, you can add a sample with some mid or top punch so your ear can find the kik. If the kik is higher than the bass, you can try adding some distortion (Sans Amp) to the bass. Just work with it until they sound good. Make sure you check both on little speakers. That helps a lot to find the higher frequencies that help your ear find the sounds. Every song is different.
(for more tips from Dave Pensado see here http://www.gearslutz.com/board/q-dave-pensado/