First, you need to leave your house, then head to the nearest police station, hold out your wrists and announce "arrest me, I'm a counterfeiter."

Kinko's

You would need the special paper that is used which has special watermarks impressed in the paper.Secondly you would need a very accurate printer,and have everything lined up perfectly.Nowadays there is a small metal-like sticker that is on the bills,so you would need to be extremely good at faking the sticker or somehow finding them.Faking the loonie would be easier for it is a metal coin representing $1.

Go buy a Monopoly game and spend it in Canada OR just use real US money.. ;)