We started making our dd stay in her bed all night at age 3 by using bribes. Every morning that she slept all night I made a HUGE deal out of it and let her pic out a few reward stickers and at the end of the first week she got a bigger reward, a barbie she had been wanting. then after two weeks she got something smaller, then 4 weeks and so forth. we did that for several weeks. we never bought anything big, just $1-5 stuff. it really motivated her. we kept a calender on the fridge and marked off the days every morning so she could see her progress. it worked immediately, the first day we started it.
at 9:55 AM on Jun. 16, 2009