Be persistent. The new found freedom of a toddler bed often leads to middle-of-the night visits to your bed. If you persistently return your child to his bed, he will learn to stay in his bed. If you sometimes allow him to sleep with you, he will continue to seek your bed. Deep sleepers unintentionally reinforce co-sleeping, because they fail to awaken. Put a bell on your door, alerting you to visitors.
Don't give negative. Or positive attention. At the same bedtime, read, brush his teeth & put him in bed in his own room drowsy, but awake to learn to fall asleep on his own without bottle or pacifier. Tell him you expect him to stay in bed till the A.M. As soon as he enters your room, CONSISTENTLY walk him back to bed from behind without talking or making eye contact. The behavior will first get worse, then cease.
Take him/her back. Toddlers can get stuck in a zone where they want you to do everyting they want & they don't understand or accept limits. Yet limit setting is important & this is a great learning project. Kids should be returned every time to their room & offered the choice of staying with the door open or being locked in. A few tears later they desire the open door & the promise of access it gives. Be firm.