We are just tackling this now with DC3 (who is 16 months old) We co-slept from the day she came home from the hospital, but now I actually want my evenings and my bed back to myself.
Our routine is a nice bath, book, cuddle, into her sleep sack, give her her teddy to hold/cuddle, milk, then I put her down in her cot whilst she is falling asleep but not asleep (this part is important)
I then pat her bum, rub her back, hum etc until she falls asleep and then I escape. For the first few nights, she would scream as soon as her head touched her mattress and stand up. I would pick her up and cuddle her when I could see that she was really upset, but otherwise I just patted her/kissed her hand/talked to her and comforted her without lifting her out.
The first few nights were really tough, I won't lie. We are now about a fortnight on and she will go into her cot and lie down and fall asleep with minimal support. She still wakes maybe 2 or even 3 times a night, but is no longer hysterical when she realises where she is and will either put herself back to sleep or just need a quick pat/kiss from me.
It has been hard, but it's been so worth it. I actually feel like I am getting my life back!