This one is quite obvious and simple: stand with your feet shoulder width apart, bend your knees a little, and jump as high as you can. Practicing this vertical jump exercise can help you jump higher. Keep your legs straight as you jump. Practice, practice, practice.
Stand with your feet shoulder width apart. Keep your back straight and lower your upper body while bending your knees. Stop when your waist reaches the same level as your knees. This should not hurt. If it does, stop before then. Raise back up and repeat. This exercise can help you jump higher because it works your muscles that are used when jumping. If you can increase the strength of the muscles used to jump, you can jump higher. Add some difficulty by jumping from the bottom of your squat, or hold dumbbells in each hand.
Toe raises are easy and you can even do them while waiting in line at the grocery store or just about anywhere. Stand with your feet shoulder width apart. Point your toes, so the rest of your feet come off the ground. You should feel this exercise in your calf muscles. Add dumbbells to each hand for a more difficult toe raise. You can also position your toes on the bottom step in your home, so you can allow your heels to go lower than your toes and then raise them by pointing your toes.
Your core means everything to your strength. Crunches help keep your core healthy and strong. You do use your back muscles and abs when jumping, so this exercise will also help you jump higher. Lie flat on your back and bend your knees so your feet are about a foot from your butt. Place your hands beneath the back of your head. Flex your stomach muscles and raise your head and shoulders off the floor until you reach a 45 degree angle. Slowly bring yourself down until the back of your head almost touches the floor. Continue. Make sure your head stays straight by focusing on a point on the ceiling. Make sure you are not bringing your chin closer to your chest, because you will then be working your neck muscles instead of your abs.
Jumping rope is an exercise that helps you jump higher because you are jumping when doing the exercise. Hold either end of the jump rope with each hand. Place the rope behind your feet. Use your wrists to swing the rope above your head and back to the front of your feet. Jump over the rope with both feet. If you have never done this it will take some practice.