Unfortunately good jumpers are born, not made. If you don't have a high ratio of fast twitch fibers, you'll never be a good jumper. You could take someone with a low percentage of fast twitch fibers, and start from birth. Give them the best coaches and trainers. Feed them all the best food. Have them exercise 5 hours a day. You might make them into a slightly above average jumper. You could take another person, like Javier Sotomayor (who high jumps almost 8 Feet) at birth, feed him potato chips and beer, have him sit on the couch watching Oprah until he's 35 yrs old, and he'd probably out jump the first guy. With a couple of months training, he'd probably be high jumping over 6 feet, which is way above average. That's just the way it is.
Having said that, the way a poor jumper can progress to a fair or average jumper is to do a lot of plyometrics.
Hate to rain on your parade, but don't want to give you false hopes. Good luck with it.
---Trainiac!