E.L.
My 2 yr old was doing the same this past summer. After trying many techniques from the continued "walk them back to bed" each time (which didn't work at all since she was still getting attention), to letting her cry/get all upset that we leave her in there, the only thing that has actually worked was a reward type system. We started giving her stickers for each night she stayed in her bed all night to put on a calendar and when she got 4 stickers, she got an extra special treat (her fav. is going to the movie theater). She also did get mini-treats with each sticker (e.g. watching a home movie)to help her not lose sight of the point. You have to keep at it though-it was hard for her to get 4 stickers in a week in the beginning but now she does without a problem. It also helps them get familiar with a calendar and day of the week. Hope this helps, good luck.