I agree with what the others have said, and have some other thoughts.
Practically, self-reflection is a key activity for Christians in all aspects of their life, hence the examination of conscience. After many years of being oblivious to the problem, and then a couple of years of strong spiritual development, I know myself well enough to know where my weaknesses are (I am now 25). For instance, if I am dehydrated, have eaten poorly or not exercised, or have become bored, then I am more likely to succumb to thoughts of lust.
I think for boys in particular, they must come to realise that lustful behaviour (particularly when they are alone) is as much a bad habit as a biological drive. I still struggle, but (through the Spirit) my behaviour is changing e.g. I don’t have music video channels on ‘in the background’ while I do other things any more, and (I hope this isn’t too personal) I don’t sleep naked any more. Little changes like this help prevent situations where unhelpful thoughts or actions occur easily.
Also, realising that chastity involves gaining something great, not just giving up something pleasurable, is a key. Since my behaviour has changed, on the mornings when I awake after a ‘pure night’s sleep’ I don’t feel groggy and lethargic, as I would if I had had an ‘impure night’. Indeed, I feel great, and some days I’m so full of energy that I get everything done I had planned to do by mid-afternoon! Obversely, after an impure night, I don’t get started until mid-afternoon. Good habits breed other good habits, and bad ones breed bad.
Likewise, because my desire for sex as an end in itself has lessened, my desire for love has increased. I am still attracted to girls, but now I am wanting to get to know them better as people, which has improved my existing friendships with women, and allowed me to become good friends with others, because I’m not expecting/hoping for anything from them (not even their friendship, which is a gift). Knowing that I am deliberately not ‘chasing sex’ also means I can talk to any girl without becoming the nervous wreck I used to be, and (it seems) that I’m more attractive as a result!
Spiritually, prayer is key, and the Rosary becomes the ‘weapon’ it is supposed to be. It’s hard to be lustful when you spend so much time with the perfect woman and the Perfect Man! Again, boys need strong, manly role-models, and there are plenty of saints who fit the bill. St. Augustine, the intellectual powerhouse who begged God for chastity so that he could give it back to Him, and Ss. Benedict, Dominic, Francis and Ignatius Loyola are good too. The best for me have been St. Paul, who had a ‘thorn in his flesh’ just like me, but was strong willed enough to submit to God’s will and ‘ran the race to the finish’, and St. Joseph, (often overlooked) who was a paragon of manliness - he worked with his hands, was physically, emotionally and spiritually strong (try fleeing your homeland on foot in the middle of the night with your young wife and her divine Son in tow because an angel told you to), and called by the Church “the Terror of Demons”. Come on, that’s just awesome. What boy would hear that and not think, ‘I want to terrify the demons too!’
Hope all that helps.