There are three main types of flips that you can do on the trampoline that are related to wakeboard inverts. Standing Front Flips and back Flips are the most common flips and are usually learned first by most people. A Side flip or cartwheel style flip is the other style of flip you can do on the trampoline and it is closely related to one of the most popular inverts that riders tend to learn first on a wakeboard; The Heelside Back Roll. The side flip, however, can be kind of tricky to learn on the trampoline. Let's go through a process that starts with a basic back flip, which you probably already can do, and then we will slowly manipulate your position on the trampoline into a side flip and eventually a Heelside back roll on the trampoline.
Step one of this manipulation is basically a step to get the feeling of doing a quarter turn together with your back flip on the trampoline. First lets set up some reference points on the trampoline by using the numbers on a clock. 12 o'clock is the point where you have the rope attached to a pole or tree which mimics the connection to the boat. For this first step stand so you are facing 3 o'clock on the trampoline just like you would do when you are practicing regular footed tantrums. Now do a straight back flip but when you land bounce again and do a quarter turn towards 12 o'clock, land and stop. We will use this quarter turn to work towards the side flip motion. Repeat this flip, bounce, then turn a few times to feel the turn and memorize the landing position.
Next, line up facing 3 o'clock again. But this time do a back flip with a quarter turn in the air during the flip so you land facing 12 o'clock. You can spin this quarter turn just by turning your head and shoulders as you flip. Repeat this a few times to get comfortable and memorize the movement. If you have problems with the quarter turn during the flip, don't worry, the next step will solve with the problem
The next step, step 3 of the manipulation is to stand on the trampoline and set up facing 3'o'clock but turn your shoulders and head so they are set up facing 12 o'clock so you are standing on the trampoline twisted. This will be your bouncing and take off position. As you leave the mat of the trampoline try to just do a normal back flip. As you flip backwards in line with 3'o'clock and 9 o'clock your pre-twisted position should have a tendency to untwist so you land with a quarter turn facing 12 o'clock. Repeat this to get the feeling of flipping back while untwisting on the way down.
Ok, at this point you are well on your way to accomplishing the side flip. Next, for the final step of you manipulation, stand on the trampoline so you are in directly between 12 o'clock and 3 o'clock. Then turn your shoulders by twisting your upper body so it is fully facing 12 o'clock. Now do the same back flip untwisting motion that you did in the previous step a few times to get comfortable. This in between step should feel slightly like a back flip but also slightly like a side flip. Ok, now you are ready for a side flip attempt.
After repeating the process a few times stand so you are facing 12 o'clock and try the full side flipping motion by executing the habit you just formed. Use your hips, shoulders and head to create the momentum needed to accomplish the flips rotation. As you bounce you will load up your shoulders by tilting them in the opposite direction you want to flip. If your goal is to side flip to the left, tilt your shoulders to the right as you bounce. Then as you initiate the flip throw or tilt your shoulders left, and while you throw your hips to the right in the opposite direction. These opposing forces should generate enough rotation to complete the rotation. Keeping your head facing 12 o'clock should keep you flipping inline with 3 o'clock and 9 o'clock and help you avoid any turning in the air. If you turn your head you will spin. So try to keep your head straight and facing 12 o'clock during the entire flip.
Alright that's all there is too it. Keep in mind that this process can also be started with the front flip if you are more comfortable. Just repeat the same process with a front flip as your starting point and base flip for the entire manipulation and go through the same steps.
After completing the manipulation and accomplishing the side flip put the rope in your hands to start practicing your heelside back rolls on land so you have better air awareness, control or to prepare for your first attempts on the water.