Like Supernanny says. You keep taking the kid back and back till they stay. Takes a few nights. Glad mine sleot in cribs. Never went through this. Even if they were sick they were on our floor and not our bed ever. And you do not talk to them ever during the process after the first time when you tell them to stay in their bed.
I actually prefer to sleep in my 4yod's bedroom (in her bed) rather than my own. My husband tosses and turns, snores really loudly, doesn't sleep well himself so he will wake up and get on his iPhone, he gets up to pee, gets up to get a drink, gets up to check out the front window...I don't get ANY sleep in bed with my husband.
With my 4yod? We curl up and we're snug as a bug in a rug...door shut, fan on...zzzzzzzzzzz
EDIT: How do we find "alone" time? We schedule it into our weekends when the kids are napping, or early mornings while all the house is still quiet. I tip-toe back into bed with him during those times.
What I did was put the boys on a sleep schedule IN THEIR OWN CRIB from the moment they came home from the hospital!! They gave me some trouble when they transitioned from crib to big boy beds but I stuck to "you have to stay in your bed AND sleep in your bed!" and within a few weeks, they were doing great!!
Their bedtime routine NEVER changes. They take baths, put their jammies on, have a little down time then it's off to bed. Prayers, kisses and hugs, good nights and they stay there! I am very lucky