Yoga and Hip Alignment?

I seem to have trouble keeping my hips aligned properly for poses like pyramid and three point balances. When my instructor adjusts them or explains it, I eventually get them there, but I always seem to go back to the same, apparently bad, alignment. Any suggestions for improving this at home? I guess my question is..how can I KNOW if my hips aren't aligned properly? Is there a way to "feel" that they are aligned properly?