B.C.
While i have yet to face this problem, as my son is still in a crib,and will be in one for as long as i can keep him there. This is what i myself will be doing when we do have to transition him. Take all the stuff from his crib and use it on teh big boy bed. A gate that will be locked to the doorway of his room. you don't want the little ones wondering around the house all night, for safety reasons and all. this will help deter him from coming out of his room. NO toys in the bed room. bedrooms are for sleeping and not playing. there are no toys in my son's room. Have and keep a steady bedtime and naptime routine. that way he knows that it's bedtime or naptime and will lay down. let him know that he doesn't have to sleep, but he does have to stay in his bed and cannot get up unless it is an urgent need. he will eventually get bored and go back ot sleep. If he gets up durign the night, go in and say night night once, after that, you just put him in his bed without saying anything. Leave the room as soon as you put him down. keep repeating the process, until he goes to sleep. this goes for naps as well.
well it's bath time so i hope this helps
B.