Thowing a bunch of 1's with fairly slow rotation seemed to help me out.
Once I could hit a particular jump, rotate trough a fairly relaxed 180, and spot the rotation over my spin-side shoulder well in advance of landing, I figured I'd have enough time to rotate all the way around on a 360. When the time came to hit a 360, the only thing that I changed was that I let the rotation continue instead of stalling out at 180.
Another thing that helped was bringing my legs up during the 180. I think other people have said not to do this, but it worked for me. It seemed like the pop --> tuck ---> spot-the-landing-and-extend sequence made it easy to keep the correct orientation in the air, and dropping the legs was an easy way to slow down my rotation. It also seems like using this sequence would help for 540's on up, but I've never tried a 540 so I guess we'll see how it goes later in the season.
Other people may have mentioned this earlier as well, but choosing a jump with the correct size is important as well. It seemed to me like jumps that were big enough for a fairly relaxed 180 but small enough that you wouldn't die on the landing were about right. I think that most of the smaller jumps in a park should give you enough air for this. I'd also look for jumps without much of a kick, as most jumps that really kick you up in the air will exacerbate the backseat problem.