I find the best way to optimise your work is by first referencing a song you like on several different speakers/systems. By doing this you can understand the strengths and weaknesses of the system you mix on, i.e. bass heavyness, weak lower mids, etc.
A simple trick that almost always works for me during the level mixing process is to lower the master volume of your song and listen if certain sounds mask others or if a sound doesn't come through at all. If the latter is the problem, then obviously that specific track needs a boost (of course first check for clipping).