I might be beating a dead horse, but speed and depth both affect the wake quite a bit.
As far as depth, the minimum we've found that still produces a decent wake without it getting washed out is about 10 feet. Anthing less (occasional drops to 9 don't seem to do too much harm) and your wake goes bye bye. The deeper the better, but bare minimum 10 feet. Where we ride, we are right at that minnimum depth a lot of the time. You can definitely tell when you get shallower, but not so much when you get deeper.
The speed matters a lot too. The slower you go, the bigger the wake and more push it will have, but then it gets mushy. The faster you go, the more the wake cleans up, but it loses some push. The trick is to play with the speed and find a happy medium for your boat.
Also, if you are in a river going down stream or up stream, you may have to adjust the speed as well to compensate for the relative speed of the boat in the water as the current will affect that as well.