If you don't have a mini-course you can just drive to the right of the boat guides. The skier uses 1, 3, 5 as the right side buoy and the outer boat guide as the 2, 4, 6 buoy.
Then when you come back, you drive on the right side (opposite as the other direction) and repeat. As you can see from a nice sketch below. Green one direction (up), blue the other (down). Big Arrow is the boat path, Zig-zag is the skier.