C.K.
Transitioning out of the crib was pretty easy for us. When I took my son out of the crib I put a twin size mattress on the floor. I wanted him to be able to easily get in and out bed, and I didn't want to worry about him rolling off the bed in the night.
The day I took his crib down I sat on his mattress and played with him. Because it was a fun place it was a good place (if that makes sense), so he was happy to sleep there. If he woke up at night he would usually get a toy or a stuffed animal and go back to bed. If he cried more than a few minutes then I went to check on him. A hug and tucking him into bed with a toy was usually enough to calm him down.