The order of the sharps beginning with F rise in perfect 5ths.

F.....5th.....C.....5th.....G.....5th.....D.....5th.....A.....5th.....E.....5th.....B

An easy way to remember this is the sentence :

Father Christmas Gave Dad An Electric Blanket

To find the key signature of a major key remember that the last sharp will be the leading note

Example

To find the key signature of A Major, go down 1 semitone from A to the leading note G sharp, and the key signature will be F sharp, C sharp and G sharp.

To find the relative minor simple go down three semitones from the Major Key

eg. G Major will be e minor