There are two types of toddlers in this world:
The crib climbers
The non-crib climbers
If you have a non-crib climber, keep that toddler in the crib as long as you can (at least wait until 2.5/3 years). Why? Most younger toddlers do not have the impulse control to stay in their bed all night. When they are a little older, 3 and up (this can vary for each child), they have more willpower to not go exploring in the middle of the night.
There tends to be a honeymoon period after a child moves to a big kid bed for a few weeks, and it seems like it will be smooth sailing. Often times, when the honeymoon ends, an after tuck in or middle of the night visitor may be in your future.
For the crib climbers, under 2.5/3 years, there are a few tricks to keep them in the crib a little longer. Keep in mind, the most important factor is safety first.
Lower the crib mattress to its lowest setting.
Remove toys and bumpers from the crib so your toddler can avoid using them as a step stool.
If your crib has a taller side, face the taller side out and the shorter side against a wall.
If he/she climbs:
Keep motivation low: Bringing your child into bed with you after they climb out or laying in bed with them/next to them until they fall asleep will not motivate them to stay in the crib.
Keep it boring: Do not engage in conversation. Simply say, “Stay in your crib”, keeping emotion out of your voice, and walk her back to the crib. If she is getting a lot of attention after climbing out, she will continue.
Catch her before the act: If you have a video monitor and see she is about to climb out, speak into the monitor and say “Stay in your crib.” You can also sit by the door, where she can’t see you, and if she puts her foot on the railing, say “stay in your crib” in a firm neutral voice.