Once you've done your mix and finished your automation (I can't remember the last time I did a mix without automation to keep the vocal clear against the instrumental tracks), adjust the overall vocal level so that it sounds about right (if you've done lots of automation and you're not happy to "trim" this then send the vocal output to a group track so that you can simply adjust a fader without disturbing the work you've already done).
At this point, you might want to make a quick list of what you think is important in the track - guitars, piano, banjo? Write it down.
Now drop your master fader or your monitor controller all the way so that you can't hear anything. Slowly fade-up the levels until you just start to hear the prominent parts of the track. What are the first things you hear? For most rock/pop type tracks, if it's the vocal/snare/kick drum then you're probably going to be pretty close to where you want to be. What do you hear next? If you've got a piano driven song and you're hearing the strings way before the piano then you might want to revisit some mix choices.
One quick thing to note - if you export your mix as a MP3 or other data compressed format then recheck the vocal levels before you send it out; the data compression can really mess-up the balance of the middle/sides of the stereo field, and as your vocal is almost always all (or virtually all) mid it can end up at a quite different level than you expect it to be. The same is true for aggressive loudness processing on the master - you may find that your vocal is suddenly a lot more prominent than you intended ( I usually check a mix with enough master buss gain to give me an average level of about -15 LUFS irrespective of what level I'm monitoring at).
Drop me a line and let me know that's useful to you.