Strap yourself to a wall and relax. Your arms may float away like a zombie's, but "it's really comfortable," swears astronaut Mike Fincke.
It had been a long day on the International Space Station, complete with a spacewalk, and astronaut Mike Fincke was tired. "We were sitting around the table drinking some tea, and I just fell asleep. I started floating away," he says in the video below.
Normally, the problem of floating, asleep astronauts (sleepfloating?) is avoided by tucking into sleeping bags strapped to the ISS's walls. But if you don't cross your arms, they'll hover above you, an eerie, zombie-like rest. Also, it's important that the ventilation in the ISS's sleeping quarters is effective, because, as astronaut trainer Robert Frost (not that Robert Frost!) explained in a post on Quora, "the carbon dioxide they breathe out doesn't float off -- it just sits there in front of their mouth, waiting to be sucked back in."
Here's the video of Mike Fincke describing his experiences sleeping in space: