Workout for 13 years old

you can't exercise 1 body parts everyday.. it will look ridiculous if you have a big upper body and small lower body.. do all of it, not just the upper.

When one muscle grows, it stimulates all surrounding muscles to grow as well, so doing legs would benefit you the most, as they are the largest muscle group in the body. Plus, you dont want to have a big upper body and tiny legs, thats embarrassing.

"Obsession is a term the lazy use to describe the dedicated" - Anon.
"Shoot for the stars, you might just reach the sky" - Unknown

hey, man...it can be really hard to get a good workout if you dont have weights. Thankfully theres calisthenics. These include pullups, crunches, etc. but include other, more difficult things like the elevated v-sit (I love doing this, heres a link to a picture of an elevated v-sit: http://www.drillsandskills.com/images/articles/Vsits.jpg). One thing I like to do is a one-legged squat. Its just like it sounds: a squat except only using one leg at a time.

What you should really start doing is learning to walk on your hands. Start with handstand pushups against a wall, then make your way to handstand pushups without a wall. I'm currently training to be able to walk on my hands and once I'm able to, I'm predicting a good amount of arm and deltoid strength to come with it.

I'm not gonna type out every calisthenics exercise you can do, just google it and you'll find some good stuff

also, finding things that you can use as weights can be really helpful. You can fill up milk cartons with sand, use your backpack full of books, use a suitcase, etc. as weight.

as far as eating is concerned, eat high protein, low fat. Turkey, Chicken, and Seafood meat these qualifications. Don't completely cut fat out of the diet though, you need good fat to give you energy and help you survive. For this, eat some nuts, some granola, etc. Also eat fruits, whole grains, and eat 1 dessert a week. Personally I can go a long, long time without eating desserts, cookies, etc. and it pays off because I don't have to work as hard physically to stay thin.

Once last remark: You should be pushing your reps higher and higher as time goes on. Don't limit yourself to 10 reps of an exercise (especially ones like pushups where you can't increase weight) when you can do more. Pushing yourself = growth. More weight = more growth, but if you cant get more weight, do more reps.