If you've got a good deep hole at your disposal you could start working on loops. Of all the air tricks, the loop is by far the least technical and it opens the door to all the rest.
1. Get yourself out of the trough and on top of the foam pile. This is a good move to work on by itself as just about every move you do is best started from this position.
2. Square up to the trough of the hole so that your boat is perpendicular to the foam pile. A rudder can help keep you straight, but don't dig the paddle in too deep because you'll be pulling it out of the water in about half a second.
3. Aggressively throw your weight forward to plug your bow into the green water. To me, this is the trickiest part because your bow can shank off to the side and every hole is a little different in terms of the best spot to plug your bow.
4. If your boat stayed straight during the plug you will start to feel the water rejecting volume of your bow. Stand up tall as your boat goes to vertical and reach your paddle over your head.
5. As your boat begins to peak, but before going over vertical, aggressively throw your body and your paddle forwards to start the flip.
6. Clear the foam with your head and land flat on your hull, ready for another.
Okay, that's best case scenario, but when properly executed that's how they go. It may seem counter intuitive to reach above your head with the paddle, but that's the secret to getting air. That extra reach pulls the boat out of the water when you start your flip.
The trick is keeping the boat straight and timing your flip. Too early and you will fall on your face. Too late and your stern won't clear, causing you to land on your head.
If your bow shanks off to the side, just go with it and aggressively execute the flip. You might end up pulling a Space Godzilla (corked/off-axis loop).
Enjoy and wear nose plugs,
"A river is more than an amenity, it is a treasure."
-Oliver Wendell Holmes writing for the majority in New Jersey v. New York