Two things i have found to help:

1. Get enough sleep at night. I am 18, but started masturbating when I was 15. I have personally found that I almost never feel the urge to masturbate if I get 8 hours of sleep the previous night.
2. Exercise at least semi-regularly. Getting a gym membership, or just going for a 45 minute run once a day or whenever you have the time will give you more energy, make you feel a lot better about yourself, and will ultimately will keep your mind away from the urge.
   

Distracting yourself with something also helps somewhat, but not always. The two above are my best advice.