when I did it with DS1 (nearly 8yrs ago I must confess - though it's still fresh in my mind - as it was the first time he ever slept on his own )
I did this (as recommended by my HV
Put him down, said whatever I said to him
Left him, and stood outside the door for 2 minutes.
Went back in, patted him repeated night night (whatever) and left straight away
Then went downstairs and put the kettle on to make a coffee
5 minutes later (once coffee was made) went back up to repeat the pat/shh thing - straight out again
Went down and drank coffee (10 minutes)
Back up - repeated shh/pat
Back downstairs for 20 minutes - opened wine,
back up
pour another glass of wine
back up
pour another glass of wine
etc etc.
It took neaerly 3hrs ) the first night - but he slept through. He stirred once but I hadn't even got to his bedroom door before he'd settled again
2nd night took 1/2hr (again he slept through
3rd night (and for the next few weeks) was 10 minutes (although after a week I just used to leave him for the 10 minutes as he started getting more distressed when I went back in to him.
Then he suddenly stopped and just whinged a little as I walked out of the door.