Have you got a baby monitor? I got one so I could hear DS stirring when I was in another room. I found this helped alot. When he wakes up I can hear him stirring (on the monitor) he calls out and I call back to him. That way, he tends to stay on the bed until I come and get him.

I also taught him to "Stop. Turn Around and Slide Down" - which he does now all by himself and has done so for a while.