It depends . . . rule of thumb is that if you can't feel any lift from wakeriding, you probably aren't getting any benefit, so move fore, aft, to the side, stern, etc, and feel it out. Benefit depends on conditions and on the size of the wake you're riding. It might only be <5% when riding a lightweight on a narrow ski but 20% benefit while riding on a double ski with two heavyweights in it. Into the wind, you'll get most benefit directly behind - usually about 30 cm gap from your bow to their stern, sometimes more, sometimes less. Sometimes the side wash is the better ride and sometimes it's a-stern. Sometimes the sweet spot is hard to find or not even there. It's not effective downwind in waves, of course.
Most important is for the draft-er to stay out of the way of the lead guy's boat and paddle at all costs, or risk being dropped or scraped off on a buoy.
One article below:
www.epickayaks.com/news/news/matt-bouman--wake-riding 
