Going around the circle, their placements tell you how many sharps, and flats in a minor key signature, are in that key. For example:
G – 1 sharp
D – 2 sharps
A – 3 sharps
E – 4 sharps
B – 5 sharps
F# – 6 sharps
(THEN GOING ANTI-CLOCKWISE FROM C)
F – 1 flat
Bb – 2 flats
Eb – 3 flats
Ab – 4 flats
Db – 5 flats
Gb – 6 flats
An acronym to remember this is Good Dogs Are Expensive But Fun. Then, you just need to remember where the #’s and b’s go. This is just for the Major key signature’s.