Ultimate Guitar Lesson

IX. Key Signatures

The key of C major has no sharps or flats.

Memorize the order of sharps. Each successive one is a fifth higher.
F# C# G# D# A# E# B#

The sharps are always applied in the order given above, with keys moving up in fifths as more are used. Each major key has a relative minor key with the same signature.

Sharps Major Key Minor Key  
1 G Em G major and E minor keys contain an F#
2 D Bm D major and B minor keys have F# and C#
3 A F#m etc.
4 E C#m  
5 B G#m  
6 F# D#m  
7 C# A#m  

Now memorize the order of flats. Each successive flat is a fourth higher (or a fifth lower).
Bb Eb Ab Db Gb Cb Fb

As successively more flats are applied to music, keys move up in fourths.

Flats Major Key Minor Key
1 F Dmm  
2 Bb Gm  
3 Eb Cm  
4 Ab Fm  
5 Db Bbm  
6 Gb Ebm  
7 Cb Abm