You need to be in shape before you take on a serious plyometrics program or you will hurt yourself. Your growth will probably be adversley effected too. Another thing that you have to take into consideration is what kind of vertical jumping you plan on doing. If it's for basketball where you need to have access to a quick/powerful jump, you should be doing "explosive" excercises (jump squat, jump squat, jump squat). If you're doing football or another sport where you need a high sustained jump, you should be trying to build up the muscle for peak jumping ability. Anyhow the point is that there are programs tailored for these specific jumping requirements.
Oh and as far as that site you want to base the next year or so of your life on, DiD YoU NoTiCe ThEiR TiTlE WaS WrItTeN LiKe ThIs?/?/ :crackup: That should be a red flag for ya man. It looks like most of their info was taken from insidehoops.com.
Try this:
http://www.drsquat.com/index.cfm?action=viewarticle&articleID=24
Hopefully that will give you a better idea of what you need to do before and during you're training.