Using a sample without the drums or vice versa???

Hey everybody. I've been sampling for a good time now but, I need to learn more about manipulating the sample. Sometimes I here a wicked sample but a snare is smack dab in the middle of the sample. I know theres ways of filtering the sounds. But is the technique called filtering? Is there any other techniques I can use to get only the...oh lets say guitar riff or just getting a kick from a beat. I'm using sound forge at the moment and still trying to figure out how to do this best. Any input would be most appreciated because this seems like a really important part to sampling.

Thank you very much

PEACE