Hello UG community.
My question is not about guitar, but i hope i can still use this forum/subforum for it.
It goes a little something like this:
I need to sing a back vocal in a band, so I need some instructions.
Whether you give me a useful link for back vocal theory, a useful youtube clip, or just write your own advice. Everything is useful.

So, how do I sing it? I found out that I shouldn't sing the same as the lead (yay me!). So should i sing with a 3 tone difference (up or down?), a whole octave up or down, or something else?

Help please.