@Charlie31 He is absolutely correct. Its not rocket science and watch out for people trying to get your money.
As for your case @Marc, there is no specific wait time after an offence is committed to apply for a U.S. waiver. They assess waivers on a case by case basis. However the longer it has been since your last convictions, what shows up on your RCMP report, whether a pardon has been granted or not, are things that will help you and will make your application look more appealing.
Good Luck hope this helps!