How to jump higher - increase your vertical in a few weeks
Most people are nowhere near their max vertical jump
The great thing about training to increase your vertical jump is that you probably have a lot of room for improvement. Even people who play basketball regularly probably haven't put in the proper training to jump at their maximum.
I'm going to go through some simple exercises that you can work on that will have you jumping several inches higher within a few weeks. With a full training program and proper diet, it's not unheard of to add a foot to your vertical within a year.
One thing to remember with these exercises is that if they target the same muscle groups you don't want to overtrain them by working them too hard on consecutive days. You're going to be breaking down some muscles, and it'll take them about 48 hours to rebuild themselves (stronger than the were). If you're training the same muscles every day, they aren't recovering and you're just increasing your chance of injury without working towards real improvement.
There are a bunch of exercises you can do without going to the gym. Squats without weights are actually great for your legs, and in particular the muscles that will help you jump higher.
Keep your back straight and bend down with your knees as low as you can go. Slowly rise back up. Do this 20 times, then take a minute break, then do it again. Take a break, then one more time. This is your warm up. It stretches your muscles without having to actually do stretching, which can actually be quite bad for you if done improperly.
Now try doing the same exercise except when you reach the lowest point explode upward as fast as you can. If you're outdoors or have a very high ceiling, lift your arms upward at the same time. You need to work on using your arms to help your body to lift upward. You'll also need to lift your arms if you plan on learning how to dunk a basketball. Once you land, go back to the crouch position and explode upward again. See if you can do this 20 times. You'll probably be feeling the burn at the end of this.
Now you can do some easier exercises to cool down. One easy one is to hold a weight in each hand (no more than 15 pounds each) and rise up on your toes. Then slowly go back down. Then up again. Repeat this like 20 times.
Jumping is about more than just your legs. You can work out your abs by laying on your back and slowly lifting your legs up until the are vertical. Then slowly lower them back down. Repeat this 20 times.
One of the best exercises for jumping is jumping rope. The repeated small jumping movements will work your rapid twitch muscles hundreds of times a minute. You don't need a weighted jump rope to do this unless you plan on entering a boxing ring anytime soon.