I just read another post that you might want to bookmark. It is about using equalization (EQ) when mixing music - a very common topic, but something that takes a lot of practice to get right.
See my post What Is Equalization, Usually Called EQ? to learn what it is.
People usually do too much with EQ at first. Then with experience, when you realize exactly why you are using EQ and what it's doing to your audio, you start to understand that a subtle use of this tool is how you get the best results.
One really useful reference guide to have handy when using EQ is a description of what frequencies affect what types of instruments and elements of your song.
For example, it is super handy to know that bass guitar is around 80-100 Hz, or that the human voice is primarily in the 2-3 KHz area. Knowing where the different instruments and sound "live" on the frequency spectrum is pretty important stuff.
This post (below) has a list of seven EQ frequency bands that you might want to print out and tape to something near your computer: