S.J.
My son had a hard time staying in his "big boy bed" at first. Once he realized he was not confined he wanted to get out of bed and ran-sack his room. We have a very simple but consistent bed time routine: pajamas, brush teeth, read books, tuck him in, lights out and close the door. If he gets out of bed we quickly put him back in bed, say goodnight, and leave. If he gets out of bed again we quickly put him back in bed without talking or interaction, and repeat that over and over if needed until he finally gives up and stays in bed and falls asleep. It's the same thing they do on Super Nanny. There were many difficult nights at the beginning, but we stuck with it and now he goes to bed very easily and sleeps great. Also for the first few months he preferred to still nap in his pack-and-play even though he slept in the bed at night. Eventually he was ok to sleep in the bed at nap time too. It's good you are doing the transition now so he won't feel like the new baby took his crib from him. Good luck!