ok I used to browse through threads like this all the time. I personally just started doing threes this season but really got them down over the last five times i went. Anyway, when I look through all these threads about how to do 360s or 540s i always see that people say to spot your landing or pick a place and keep looking for it. This DID NOT work for me  . . . (as a side note i feel like I may be the only one on NS with this view) when I would go for the 360 and spot my landing I always would end up getting to a little over 180  (lets say 220 for shits and giggles) and i would end up kind of flailing to make it around. I found that it is easier to just wind up hard and commit, do not put effort into spotting a landing , just go with the flow. As someone above me said, it is just like spinning on the ground really - it just takes more force. I find that I am spotting my landings now naturally and can land threes with ease. It will just click, it happened with me and a few of the people i ride with just out of the blue , we all attribute it to the fact that we just let it flow , dont think about it too much.
im not sure if that made any sense but i tried.