When mixing, I always try to get the drums/bas/vocals to be the "song". Meaning that when listening, you dont really need anymore instruments on the track.
When these 3 "instruments" sound good together and make a good cake - bring in the iceing for it - guitars, synths, backing vox etc. and mix them to taste (subtle is my best) to make the cake a little sweet, but not too much, when putting too much iceing on a cake you can ruin it, and destroy the good taste of the cake.
(I'm smoking too much weed - I know)
and a
for the heck of it.