However for this guide you will need a pair of dumbbells you feel comfortable lifting as well as a medicine ball (5 - 10lbs).
I Personally am a teenager in high school, and have lots of schoolwork to juggle as well as extracurricular activities that are not sport related.
I do not have a gym membership but working out in my room makes a big difference.
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1. Stretch - Do some really good stretches involving your legs and arms.
2. Run at high speed for 10 minutes. (Studies show that running at full or interval speeds increase your heart rate and burn as much fat and calories as running at a constant pace for 30 minutes.) <-- This has to be done outside, or on a treadmill if you have one. If you don't just do suicides (Don't kill yourself, although they make you feel like you want to).
3. The next 30 minutes are quick exercises that can be done in your room or living room.
Triceps
Dips
A) Grab 2 chairs and put them facing each other about a little less than your body length away. Place one foot on one chair and your arms holding you up on the other. Start lowering your back and upper body holding yourself with your arms. About 12 reps and 2 - 3 sets.
Chest
Push ups
A) Really simple but works amazingly on your chest (pectoralis major) and lower chest (pectoralis minor). Simple place your hands shoulder length apart and start doing push ups. With the completion of every set move your hands closer together. On your last set you should have your hands forming a diamond. About 10 reps and 3 sets.
Dumbell Bench Press
Be)Simply hold the dumbells like you would a bar. (This is very hard to explain so simply google Bench Press.) About 2 sets of 12 - 15 reps.
Abdominals
Leg Raises
A) Leg Raises work your lower abdominals, and help make that six-pack even more defined. Place your hands under your lower back and lay flat on the floor. Raise your legs together in a slow constant motion. Do a 1-2-3 count as you raise and lower keeping this tempo ensures you don't lose the burn. About 2 sets of 15 reps each.
Crunches
Be) Crunches are simple and I assume you know how to do them, the key is to not lift with your head or neck. Ensure you don't make this mistake by placing your hands - palms flat- across your chest. Maintain the same tempo as Leg Raises. If you do not feel your abdominals working Increase the speed, however don't lose your technique. Same reps and sets as above.
Medicine Ball Jumps
C) Really Easy! Simply hold the medicine ball around your stomach, bend your knees and explode up raising the medicine ball above your head as you jump. About 3 sets 10-12 reps each.
*As you can see the three excercises above all target your abdominal area, as I assume like most teenagers your stomach is your target area.These high fat burning and abdominal working excercises will get that six-pack in no time.*
Biceps
Bicep Curls
A) Really simple, stand ( in front of a mirror preferrably) and simple keep your elbows tucked towards your sides curl the weight. Breathe out whilst curling and breath in whilst doing your negatives (lowering the weight).About 3 sets of 10-15 reps.
Hammer Curls
Be) Whilst seated simple hold the dumbbells like hammers, with the ends facing upwards and downwards. Simple curl the weight slowly, isolating the bicep. Same Sets and rep as above.
As you can notice my main source of leg stengthening in this guide is running. However the next excercise is easy to do but I don't recommend using a floor that can be damaged easily. It also requires a partner to aid you.
Legs
Dumbell Leg Flexion
A) Dumbell Leg Curls are fairly easy you can use the same weight you're curling assuming your legs are as strong as your arms. Do about 2 sets of 12 reps each.
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These excercises each target a designated area that is bolded. Feel free to mix any a, be (be because b is a smiley face) and c excercises. Stick with the same combination for 2 weeks then mix it up again.
Soon you'll be looking good and the envy of many friends who are too busy playing their X-Box's. With this way you can listen to your music, or watcha tv-show whiles excercising your body.
**Legal Disclaimer - Please don't expect Bowflex bodies in less than 2 weeks to a month, those machines cost insane amounts of money and take up space you probably don't have. These excercises are for those without gym memberships and working out in their rooms or houses. I guarantee however you will see results in atleast 1 month and a half. You will notice definition.**
But great guide and keep it going! 
which we had to do for an hour or so after which we were allowed to start kicks and so on. But nowadays to prevent the notorious lazy bottom disease from hitting my system I jog with my dogs twice a day for half an hour and also occasionally play badminton.
