Well, I find the best way is to put the backing vocals, including yourself, if you use overdubs, on a good, but less detailed mic. For main vox I use B.L.U.E. Kiwi, Rode NTK, and Studio Projects C-3. For backing vocals, I use Shure SM7, Shure SM57, and Oktava MK319, depending on the tone profile of the singers voices.
Want them more in the background? Here's a clue- Turn the bitches down! Didn't your momma raise you right? That's why God gave you faders. Then there's plan B. Get singers that rock, and delete yourself. They may not be in the background, but at least it won't suck.-Richie