This shows what chords are in each key... it's kind of basic
KEY : Chords in Key
Ab or G# : Ab, Bbm, CM, Db, Eb, Fm, Gdim
A: A, Bm, Dbm, D, E, Gbm, Abdim
Bb or A#: Bb, Cm, Dm, Eb, F, Gm, Adim
B: B, Dbm, Ebm, E, Gb, Abm, Bdim
C: C, Dm, Em, F, G, Am, Bdim
Db or C#: Db, Ebm, Fm, Gb, Abm, Bbm, Cdim
D: D, Em, Gbm, G, G, A, Bm, Dbdim
Eb or D#:Eb, Fm, Gm, Ab, Bb, Cm, Ddim
E: E, Gbm, Abm, A, B, Dbm, Ebdim
F: F, Gm, Am, Bb, C, Dm, Edim
Gb or F#: Gb, Abm, Bbm, B, Db, Ebm, Fdim
G: G, Am, Bm, C, D, Em, Gdim
This chart will allow you to take what chords are in a progression and find what key it is in. This will come in handy for awhile until you get use to it. You will start knowing just by the chords what key a song is in. G is by far one of the more common Keys for songs to be in... There ys Go!