I had the same problem learning them to fakie. Just make sure you jump high enough to get a full rotation of 180, so you land exactly backwards from where you started. Compress a lot too. I suggest learning to fakie good first too. Go up a little bank or something and do a little stall and come back in fakie and just see how long you can get before you fall, then after a good distance is consistant and you can fakie nice and straight and you can correct yourself. After you have those practice getting out of a short fakie. Try sliders first then move on to half-cabs. to slider just turn your front wheel to the side you 180 towards and pull your shoulders around while leaning back just enough to let your front wheel slide. Half-cabs are just a 180 out of fakie. Harder to half-cab.