1) they know their scales
2) they know more than one instrument
3) they dress funny.
Now on to the dry stuff: I needed to find printable scales for a student to practice from. Using a book for this is a sure way to kill the binding, so a few pages printed is worth the effort:
Major Scales Chart
(except Ab, go here for that one)
Natural Minor Scales Chart
Go here to view images of keyboards to see which keys to play
in either major or minor scales.