I like the supernanny suggestion that was made. That method does work. In addition what i have done was several things depending on the situation. If feasible, I have started the bedtime routine earlier. My kids' normal bedtime is 7. So if they were staying up late playing I would make their bedtime at 6. This really only works best in the dark winter months though.
Also we have physically sat outside their rooms because they would try and sneak out to play in their siblings room. Usually my hubby would sit in th hall with his laptop doing his work and periodically warning them to go to sleep. This worked better around 2 1/2 years old.
We just moved our 23 month old son to a big boy bed. So far so good. Once or twice I have returned him to his bed with a firm voice and body language that said "don't even think about it Mister!" We do let him play with his computer toy and trucks and books by the light of a little night light. Then when it is absolutrely time to sleep I go in and turn the night light down or off - whichever his mood will allow. Then I tuck, kiss say I love you, Sweet dreams & God bless - all of which he repeats (again when his mood allows) so that we both know this is it!
It is physical work in the beginning, but it won't last forever. Soon enough the newness will wear off and exhaustion will creep in and he'll go to sleep without much difficulty - that is if you do not let him make the rules. Be firm. Be consistant.
A.