C.T.
My daughter transitioned when she was 2 yrs. 3 months old.
I had read somewhere that you should tell your child that they are not to get out of bed until you come get them.
The first night we gave her 2 stuffed animals and 3 books. I told her she was not to get out of bed and made her respond by saying "Yes Mommy." We followed her normal night routine.
Then I watched her on the monitor. She got out of bed twice. Each time, I went in there and told her that she needed to stay in bed and that she was not to get out until Mommy or Daddy came to get here.
This went on for 3 nights on the 4th night she got it. She rarely gets out of bed now and stays in her bed just as if she was in her crib.
She just moved from a toddler bed into a queen bed (I put rails up) and the same rule applies. I am a little more flexible on her getting up since we are potty training. She is now 2 years 8 months old.