Leaving the crib behind is a major milestone of the toddler years. In the interest of a seamless (or, somewhat seamless) move, we turned to developmental expert Dr. Aliza Pressman of Seedlings Group (a been-there-done-that mom), who shared the scoop on exactly when and how to make the big transition.

Three is the magic number. Dr. Pressman strongly encourages waiting until your child turns 3 to make the move, then enforcing a “Don’t get out of bed without your grownup” policy—something by which younger children won’t be developmentally capable of abiding.

One thing at a time. “In general, you want to avoid more than one transition in a 6-week period,” says Dr. Pressman. So if you’re in the midst of potty training or they’ve just started preschool, wait until things have settled down to make the move.

Be wary of new sibling timing. If you’re graduating your toddler to a bed because a new baby is on the way, do not make the move about that. Separate the two in your older child’s mind.

Consider personality. Some children need a few days or a week to process a big change on the horizon, while others will do better finding out immediately before the switch. Break the news accordingly.

Transition slowly, if need be. Dr. Pressman says it’s fine to start out with the crib and big kid mattress in the same room, and/or alternate between the two for naps and bedtime at the beginning.

Bring it down to their level. Enlist a book like Sophie’s Big Bed to explain what’s happening.

Stay positive and patient. As with much of early childhood development, positive reinforcement is key here. Reward the nights that she stays in her own bed with lots of praise, and keep your cool on the nights she doesn’t.