We started this about two months ago when our oldest was about 2 1/2... we created a sleep rules poster.  I found the idea at parentsconnect.com. Here is the link:

http://www.parentsconnect.com/articles/weissbluth-sleep-setting-sleep-rules.jhtml

On the poster we made, I took photos of him for each rule and also a photo with him holding his reward jar.  We reviewed the rules each time he went in for a nap or for bed.  I'm not saying he's perfect now, but before he would jump out of bed and run to the gate at his door over and over again.  Now, if he does get up, he usually stays there for a little, and then gets into bed on his own (at night... naps are another animal).  But, I found that this did set up specific expectations, and broke the cycle of him not staying in bed.  Hope it helps!