I'm a beginner Flowrider, as I'm still working on my balance. But I like to push the envelope and try new things. First time I ever tried it was in Massanutten, when my family when to the water park for a day. I thought it looked cool, but didn't try it until late afternoon. All the riders were young teens, so what's an old guy going to do on a Flowrider? Found that I instantly fell in love. Was quickly up on my knees, and trying (and failing) new stuff. But it's all good.
So here are tips for new riders:
Don't ride too far forward on the board, you're more likely to catch the front edge, or turn sideways.
Use your toes (into the water) to keep yourself pointed forward. The drag will keep you aligned, or use one foot at a time while you also pull up a little on the board to start working on your turns.
To pop up on your knees, grab the board near the MIDDLE. Too often I see people try to grab it too far forward, then they'll push the board down into the water and lose it. If you push it in the middle (on the edges) it will support your weight as you pop up.
Once you start to improve your balance on your knees, you can lean back more and work on your balance. You can drag your hands a bit for stability, or to start thinking about future moves you might try.
One new trick I found I could do was stand up on the matt in the middle of the flow (although one safety rep yelled at me for doing so.)
Any experiences riders are welcome to correct anything I'm saying here. I don't really claim to know much about riding, but wasn't able to find much online, so thought I'd provide a little info for anyone that was looking for it. Hope this helps you too. Enjoy!