Hey there! I'm happy to help!
1. Education - using programs such as DARE in schools to inform students about the dangers of drugs and how they can be detrimental their lives will greatly discourage drug usage among youth. Having youth commit to being drug free is very empowering and will lead them to want to discourage their peers as well.
2. Drug Testing - many youth might use drugs such as steroids to gain physical advantages with sports. If the education strategy doesn't work, having drug testing for sports will discourage youth to use harmful drugs because if they test positive they will not be able to play on the team they want to.
Have a wonderful day and keep on learning! :D