tracey-
do you have a "pro' release recording, of a section of a song that features a bass sound that you really dig?
if so, take it and run it thru something like HarBal, or SPAN
just the bass, as much of just a section of bass to help isolate it from other instruments......
look at the eq curve, and figure out why it is what it is.
that is KEY to beginning to learn how to carve a nice niche for you bass.
now, this wont be the same curve for every song...... even with the same bass.
because the other instruments come into play...
the arrangement comes into play...
your choice of processing (limiting, compression, eq and even panning) comes into play.....
but you get the idea.
what you want to do, is have a full bass, but get rid of problem areas that cause build-up, or step on other frequencies within the song.
guys build entire careers, on just being able to dial in their bass, because after that, the rest is cake!!!
(yeah, sure.)