Cut (EQ) everything that does not need to be there. Do this excessively! Make a plan of things you want to hear in each frequency range. Like kick and bass, then guitars, leave room for some vocals in the midrange, then guitar sizzle, keyboards, cymbals and don't forget the snare. Cut everything away that does not belong the planned frequency range, use steep filters CUT DEEP and do not dip a little bit. This needs some practice, but if you do it right you will notice a huge improvement of your bass and low midrange clarity. As a side effect, your mix will get louder and tighter which leaves room for some serious master bus compression and limiting to compress the hell out of your mix, as everybody does nowadays...