Okay guys, Im a song writer..So I write my lyrics then put chords to them.

Say..its a simple song...3 chords...G C D...The key I'm playing in would be?

Or say its...F C G..What would the key be?

I need to know how to find the key in a progression.

I know alot of scales, Major and minor pen. Along with alot of the blues scales. I can come up with licks out of these scales but have no idea how to put them to chords and make it sound right "in theory".

These are the problems im having. Can any of you point me in the right direction?