Wake jumps - how to land on both feet?

I tried wake jumping for the first time last saturday and landed the first 3 ok. On the fourth try I landed one foot on and one foot off the board and sprained my knee.
So what's the trick to not getting screwed up on jumps? What do you focus on? Any tips will be greatly appreciated. I'm kinda nervous about trying it again. But the first couple attempts were so much fun!

Suck the board up with you. If your back foot came off you probably kept your front leg straight. That will push the board out in front of you. It just takes time. Good luck.

Thanks Spencer. I'll concentrate on that (when the knee gets better!).