EQ is one of the most important parts of mixing. It helps you acheive the balance and effect you're looking for. Unfortunately, there are no hard and fast rules for using eq in your music which makes this a bit of a difficult skill to master. I've been mixing music for more than 15 years and have learned and experimented a lot in that time. I'm going to share some tips with you that will help you get to better mixes.
I was recently in Atlanta visiting family and scouting places to grab some quick photos for my artist portfolio (which both artists AND producers should have) when I came across a GEM... Krog Street Tunnel
A compressor is a device or software designed to reduce the gain of a signal once that signal hits a pre-set threshold. This also reduces the dynamic range of that signal (dynamic range is the difference between the loudest peak of that signal to the most quiet peaks.) While that may sound like it'll make things less exciting it's actually a good thing because it will lower the louder peaks and even out notes that might stick out so that you could bring up the over-all volume on that signal while minimizing the chance of it clipping.
Mixed in Key has come through with a real game changer. A cross platform plug in that lets you share your session with collaborators with out having to export and email stems.