It'll vary with each sample, and remember that EQ is to shape whats already there, not to create sound. If you have a sample that has nothing worthwhile around say, 100hz, then boosting there with EQ wont add anything extra to the sound, you'll just be making unimportant bits of it louder if that makes any sense.
A good way to start, is to set up your EQ, set a narrow bandwidth/Q, with quite a lot of boost (enough to make an obvious difference), and sweep through the whole frequency range. It'll become obvious which parts of the spectrum are important frequencies that help your sample hit nicely, and which parts are needless. You can then make your decision of where to cut or boost from that.
It'll become more obvious the more times you do it, and you'll start to get a good idea of whats going to work just by listening.
