Depends on wether you're doing the parts separately or all at once.
Obviously you can have a bit more control if you do them separately, like adding individual compression, tuning, and effects that you don't want applied to all tracks.
Last week I recorded a bluegrass band and we did a couple takes of all 4 of us singing harmonies. Then we layered it with individual takes of the better (more pitch conscious) singers and make those tracks a little more prominent in the mix. In the end it sounded like 16 people singing, but there were 4 distinct vocal parts.
I added a little bit of hall reverb, panned the individual parts: 1 hard left, 2 50% left, 3 50% right, 4 hard right, had the group parts panned from 50% left to 50% right. We ended up with a really cool wide sounding vocal harmony.
Hope that helped.