Baking Projected Textures

I need a Tutorial on baking textures into UV space.
Sometimes I can get the Open GL UV render to do it, sometimes it wont.
I've never got it to do it by purpose .
It seems like i'm missing something or buggy?
Any help would be great!!!!
Thanks so much
Sometimes I can get the Open GL UV render to do it, sometimes it wont.
I've never got it to do it by purpose .
It seems like i'm missing something or buggy?
Any help would be great!!!!
Thanks so much