just a question- does harmonizing voices work the same way as with guitar- you know 3rds, 5ths, octives, etc? cuz right now ive been doing all of it by ear, sometimes sounds good, sometimes....not as good.

any pointers?

Yes, you can harmonize that way. You can harmonize by forming chords. Any way that is theoreticly correct with other instruments can be applied to voice. I think some of the best vocal harmonies were done by the Eagles. Simon and Garfunfle sold a few albums too.