How can I stop falling sleep during meditation?

Bal Zs X.
While I don’t know when and in which position you meditate, you could try meditate sitting at the time when you feel the most alert.
If you are already doing that, then it’s a good opportunity to practice acceptance, and try not feeling bad about falling asleep.

Jessica U.
I find it's helpful to sit up or even do it while doing another activity–just one activity though–like walking out even taking a shower. Then when you start at clearing your mind in those spaces then you can sit/lay on your own. Remember, just doing it is what's important, no matter if you fall asleep or not. =)

Alyssa W.
I find changing my body position is what makes the difference. If I lie down be it on my mat or the bed I am more likely to fall asleep. If I sit on the floor I am more likely to stay awake. Also, focus on something: your breath or a noise in the room (fishtank, air conditioner) instead of the "let your mind go blank advice we sometimes get. That's what works for me.