The single handed most important exercise is jump roping. There isn't or hasn't been a boxer who doesn't jump rope. It improves foot work, stamina, and increases leg strength which increases punching power. Master jump rope and you'll be a better boxer. Especially at a young age it will give you quite the advantage.

best practice for speed is hit a body bag fast as you can but hit it where it doesnt move make it like a whip fast full extension but controlled and best practice for jab do the same but jab once then jab twice then 3 times then 4 then go all the way up to 20 then back down so like this... 1 = 1 punch (1, 11, 111, 1111, 11111, 111111) so you should punch 210 times going from 1 to 20 and 420 going 1 to 20 then 20 to 1

There is a technique that Mohammad ali used is to got to the local pool and punch while your in the water,this will increase your power for the punches and the speed or you can punch a punching bag and imagine its your opponent. i am 14 and i do boxing too and these techniques helped me alot.

If you are really serious about getting into boxing then have your parents help you look for a decent boxing gym in your area. Sign up for a few lessons and see if you still have the bug. If you don't then at least you will have learned some basics had have some advice on which exercises will help in which areas.

I am a 14 year old guy and I would really like to get into boxing. Are there some exercises I can do to increase my speed, power of my punch? stamina, etc.? Also my form of my punch too.