Not falling asleep

I've been trying to astral project and have separated twice now. It seems like anytime I'm conscious during the vibrating state, I know what to do and can separate, but it's getting to that state that's the problem. Ive tried disrupting my sleep schedule (sleeping for four hours, getting up for an hour, then going back to sleep) which worked one time, and going to sleep at an abnormal time, which also worked one time. But most of the time I just fall asleep. I can't put my finger on how I did it successfully . It was like, I fell asleep, then boom, my conscience kicked in and I'm vibrating. I haven't been able to meditate my way to the vibrational state, it's just like I checked out for a little while, then checked back in once my body was asleep. For those of you who have had lots of practice, how do you stay conscious? I can't help but feeling like it's more of a chance occurance than something I have control of. I've heard of the arm exercise, where you keep your arm up so it wakes you when it falls, but I don't really like that technique..any other techniques?