Want to clean up your mixes? A great way to start is to prepare your tracks by adding a highpass filter and adjusting it to remove low-frequency garbage — hum, rumble, room mud, and other unwanted low frequencies below the desired signal. Just switch the HP filter on, adjust the frequency until you can just start to hear it affect the low end of your audio, then lower the frequency until you can’t hear it affect your desired signal when you switch it in and out.
This trick is particularly useful for tracks recorded with mics, but will also help synth and sampled sounds with unwanted low-frequencies. You’ll be surprised how much it will clarify your mix and restore headroom.