always do what sound best, that is the golden rule, but how do we make it sound it's best is the rub.
Some general ideas for voice leading: don't just consider the two chords I to V or whatever they are but the progression as a whole. the idea is to have the voices moving in a manner that is pleasant to listen to (or unpleasant if that's what you're going for). especially the outer voices ( the lowest and highest note you play). they should always move in a logical way (usually without any jarringly large jumps), however if the effect you want is achieved without following these "rules" by all means have at it. using inversions and extensions ( 9th,11th 13th b9, #11 etc...) make the creative possibilities endless and that's the beauty. experiment, practice and have fun.