One thing that helped me a ton was to learn the difference between "loudness" and "level".  You have to manage the loudness of your track with your ears and with a good meter (I use the Melda multi-analyzer but I think Ozone has one as well).  I spent too much time trying to keep my master under 0db thinking that was good mixing and then getting really thin mixes even with a peaking master.  The truth is that you want to have really consistent loudness in your track so that all the loudest parts are pretty similar and that the quieter parts are a pleasant counterpoint.  Some tools for that are obviously compression and make-up gain but you have to use those wisely and adjust them throughout the track-- don't just slap them on.  You can also start add or thin your musical elements to compensate for their relative loudness too.  Crank the synth when it's all by itself but back off when it sits with your kick,bass and arp.  Does that make any sense?