How old is he?
Do you tell him that '10 minutes till sleep time' etc etc.
The sleep nurse gave me that tip and I used to say it to ds2 since he was around 3 months old.
Then wen it was time to go I'd tell how I was going to close the blinds, wrap him up and so forth.
I do think it helped somewhat.. Sometimes it can feel a bit silly talking to a baby but I'll try the same for no 3 in a few months time.