I found an awesome site called crossfit.com-I swear I dont work for them either-they post a WOD workout of the day-its only like 20-30 minutes and it will knock you on your ass-it will help for inverts abs arm strength every muscle you need to get better on the water-it worked for me-Some of the exersises you will have to substitue your own but i saw a big improvement in my riding after a month of this site-try it.

yup, exercising and stretching are two key factors to get better at wakeboarding... the others are practice and and trying new things every set.