First of all, you don't need an ultra fancy camera. Here is what I use for 100% of my levitation shots:
When I'm taking the picture by myself (which is 90% of the time), I set up my camera on a nearby ledge or my "tripod":
Levitation shots are the same principle as jump shots. But it's a rhombus/square idea. All levitation pictures are jump shots, but not all jump shots qualify as levitation shots. The difference is the positioning of your body. If you want it to look like you're floating, you have to look relaxed. Here are a couple tips to help:
1). Set your camera to a fast shutter speed or high iso -- it's all the same technique as getting a good action shot.
2). Having a lot of light helps the picture from coming out blurry. If you don't have enough sun, try a flash (although it can create a washed-out effect, sometimes that's cool too).
3). Most of the battle in looking relaxed is in the arm positioning. If your arms are stiff, it looks like you're just jumping. Relaxed arms help.
4). Another thing that helps you look natural is the angle of your body. Even having a slight angle forward can make you look as if you have a destination.
And here are a few hints from personal experience in the last few months of taking levitation pictures:
1). I use a double jump to get more height. It can be hard to get a good jump when you're going straight up, so I do a prep hop to help me spring into a higher jump for the actual levitation shot. If you're having a friend take the picture (which often can make the whole endeavor less embarrassing if you're taking the picture in public), this can make the timing coordination easier for them as well.
2). If you're taking pictures in a public arena, try to avoid shops that sell delicate items. Shopkeepers tend to get antsy about you jumping around and flashing photos (for good reason).
3). For girls with long hair -- this is another added factor. When you're first starting, I'd advise tying it up until you can get some good consistent levitation shots. In order to avoid the whole "hair blowing everywhere" effect that jumping often induces, you should get the camera to go off while you're in the upward trajectory of your jump. The double jump method that I use helps give your hair a little bit of volume (if you want) so it's not completely flat in the pictures.
4). Shoes make a difference. I love how heels look in the pictures, but my Vans get the best height and produce the most consistently good levitation photos. It's almost impossible to take a good photo in flip-flops because your feet automatically scrunch to keep them on (and look very stiff). Basically, any shoes you'd be uncomfortable going on a rollercoaster in are a bad idea. Every one less factor you have to think of while taking levitation photos makes it that much better.