Replying to 360 Help?

I've been skiing for about a week now and I can easily get 180s and ride switch, but when I try to 360 I get to around a 180 maybe a little more and then stop committing. I have this other problem also that could affect it a little bit so I start spinning the opposite way before reaching the lip and this causes my skis to get tangled up. I've been trying 360s in my backyard mostly, but I have access to a bigger hill if needed. Any tips for landing them and getting rid of my problem of spinning early?