1. yeh, eat more often. now, if i haven't eaten anything in 3 hours i get really hungry. try spacing your meals out like that.
2. eat better food. stay away from chocolate; eat fruit instead. instead of cereal, eat oatmeal - i love that stuff now; first time i ate it i puked. go for complex carbs (like pasta, rice, bread, potatoes) instead of simple ones (fruit) during your main meals.
3. drink more water. much more water. no more fizzy drinks. water helps transport the nutrients from your food around the body more efficiently, which enables you to eat more often (every 3 hours). just now, i'm drinking at least 3litres a day. aim for 4. stop drinking fizzy drinks
4. drink more milk. have a look at the nutrients on the back of a bottle of milk. 3.5g protein per 100g. 5g carbs (simple sugars mind you). how much better is that than a can of coke? a lot better
when i was 15, i was just under 8 stones (50kg), skinny as shyt. i knew i was a skinny bastard and so did everyone else. i didn't do anything about the problem though; i still ate chocolate for lunch, crisps for lunch, hardly had any breakfast, drank 4 litres of coke a week. my diet sucked so much. now my diet is better than 95% of the population - and so is my body. i just wish i had started eating better sooner - my high school life would have been a lot better