I've been playing guitar for a while but I've never been really educated as far as things like this. I mean I know stuff like major min. and dim. but yeah..
D major (tonic), A major (dominant), B minor (tonic relative or submediant—the relative minor tonic), D major in first inversion (tonic with the third as the lowest-sounding note) or F-sharp minor G major (subdominant), D major (tonic), G major (subdominant), and A major (dominant)
It depends on what major and tune, try going on http://funadvice.com/r/14oebij7bpr they have great choices there.
I always play a G, then a C7, then a D to help my fingers warm up before I play