I have to agree with the individual who stated that you are still a little too young to do too much and should wait and try to let nature take its course a little more first before getting into strength training in earnest. There are, however, things you can do in the meantime to prepare yourself for more extensive strength training in the future:

At your age, there is nothing better than eating healthfully and taking care of yourself; don’t do like I do and hunker down with a bag of potato chips and a Coke to watch a game! In addition, get enough rest, exercise, and drink all the HEALTHY liquids you want like water and fruit and vegetable juices! Avoid my Cokes! They’re MINE! 🙂 Or at least drink sweetened stuff like them in moderation – it leaves more for me because I’m over the hill anyway!

However, please don’t think that you can’t train with weights at all now – just do so in moderation with light weights so you don’t damage yourself while you’re still an your growing stage. While you are still young and flexible, simply use light resistance weight so you are able to focus on the PROPER FORM to get the benefits that those particular exercises should bring you. Don’t be stupid like way too many people whom I have seen who try to lift too much weight before they are ready! Thinking that the more weight you lift, the sooner you’ll become buff is a recipe for disaster – I guarantee it.

Unless you want to end up with a herniated disk or other problems at fifteen or sixteen years of age, simply take it nice and slow, ask for help from someone WHO REALLY KNOWS WHAT THEY’RE TALKING ABOUT, and follow their instructions faithfully. You should also read books or articles on the topic of weight training, and LEARN YOUR LIMITS!

The strength will come as you learn to perform the repetitions properly and add additional weight as you go; all you have to do is LEARN TO TRAIN WITH WEIGHTS CORRECTLY!
BEST OF LUCK! 🙂

I ALMOST FORGOT! STAY AWAY FROM STUFF LIKE STEROIDS!

I used to help various people train with weights back in the days right after they decided it wouldn’t turn normal people in muscle-bound troglodytes…

sit ups

push ups

pull ups

curls

crunches

running

….

you should know the rest…