Past mistakes can't be taken away the only thing you can do is move forward.
what you can do:
-let time pass
-Try to get involved in volunteer work (i.e. auxiliary police, volunteer firefighter, etc) to show them that you have matured and take part in activities that show responsibility.
If you had an experimentation with marijuana 60 times then you would have a problem 1. because that is way to much 2. 60 times is by no means experimentation. 2 times with marijuana usuage will not ban you from this field and every department has different guidlines regarding drug use (frequency, type, and last time usage). Check with the dept you wish to apply to and see what their policy is on drug experimentation.
GOOD LUCK.
Who ever said dreams don't come true?
NYSP-2/14/05