I'm relatively new to the whole recording/mixing world, but I have read up quite a bit on the process and experimented with what I've learned.
My band recorded a demo, and the quality was pretty crappy. The studio guy had fairly decent equipment, so I was expecting some pretty well recorded tracks. However, I was wrong, and thoroughly disappointed, as the result was very, very lame. So I was forced to fix the recordings myself with my limited access to good equipment/software.
Anyway, moving along, since I am a bass player, I concentrated on making my bass playing stick out and have a good tone. The key to this, as many have mentioned, is compression and EQing.
The studio guy had compressed the bass track before I got access to it, so I didn't really have to compress it again to get more headroom. I then shifted my attention to EQ. I first found the frequency range of the kick and the snare, and then cut a notch in all the tracks out of those ranges, which helped the drums get some definition.
Then I experimented with a paramentric EQ by keeping a constant Q and gain boost while sweeping the center frequency to find friendly and harmful frequencies. One advantage that I had was that since I am a bass player, I have a pretty good idea of how different frequencies affect your sound, so I had kind of a head start. To sum it up, here's more or less what I did in terms of EQing my bass track:
1. Roll off frequencies below 40ish Hz.
2. Cut a small notch at 66-70 Hz (the kick).
3. Cut a small notch at 160 Hz (snare).
4. Boost (with a parametric EQ) in the 80-85 Hz and the 120-250 Hz regions (this gives punch and growl). Be careful, as boosting too much here can really eat up headroom and muddy up your overall sound.
5. Cut in the 300-550ish Hz range (boosting gives a honky sound, which I don't like, and if you overdo it, it'll get really muddy and interfere with the guitars).
6. Boost at 800 Hz. This is the "magic" frequency for bass, because it gives definition and some power to the track and really helps it stand out.
7. Boost 1.2-1.6 kHz a tad to get some more clarity a bit of the percussive effect.
8. Roll off the super highs, because they're only eating up headroom and don't really help too much (just like everything else, listen to what you're doing to avoid overdoing it).
For the frequencies I boosted, I cut a notch out of the other tracks so that there was no fighting over that space between the different tracks. A couple of times I overdid some of the boosts, so I had to use compression to tame it down (multi-band is great for these purposes). I used compression instead of EQing those frequencies out because compression helped control dynamics, which is what I needed, rather than changing the sonic character, which is what the EQ was doing.
These steps may help you out a bit, take them with a grain of salt, as what works for me may not work for you (not to mention that I'm pretty new to all this). Also, remember that the best way to get something to stick out more is to see how it sits in the mix in relation to others. Before I had learned about "carving out space" for different instruments, I would just EQ the specific track and not get anywhere. But when I started manipulating the other instrument tracks carefully (again, don't overdo it, or you'll change the sound of those tracks), a little bit got me very far.
While the mix doesn't sound as good as I would like it to (I had very limited time with the equipment and all), the bass does stand out much more than it initially did, you can actually the individual instruments. A friend commented on how the bass sits very nicely and distinctly in the mix, which was nice to hear. If I had more time to mess around on the mix, and had the intial recorded quality of the tracks been better, I know I could have done a better job. But then again, we can't all get what we want, and we have to start somewhere.
Anyway, good luck, and don't give up!
You, my friend, have a definite future in the recording world. Stick around.
