I agree with what Julesy said bout age and personality being a deciding factor, plus what you feel comfortable in doing.
Our DD would never sleep in the day she would scream, we would cuddle her or stand and rock her cot for like 45-60mins til she fell asleep, it was a nightmare for me and her cause she's get so tired she would be beside herself.
We then did a comtrol comfort where we left the room and when she got upset went in and patted or cuddled if she was really upset but when she calmed down left again. This worked by 2 days and we learnt that our DD settles better if we aren't in her room constantly. I always thought it was wrong to leave the room until I made sure she was asleep because she would get upset if we left. But we learnt that whenever we stay in the room she gets even more upset then if we leave cause she just wants us to pick her up, which we just physically can't do constantly.
Now we put her down, she grizzles for awhile but happily goes off to sleep and we have found that she is much happier during the day and feeding better because she is not so overtired.
This worked well for us but may not work so well for another child.

I hope you find something that works for you and your son. Maybe try to have a little ritual before all sleeps so he knows. Like ours is putting her into her sleeping bag for all sleeps, cuddling while I have the CD on in the back ground and then giving her her little toy that i just give her in bed so she learns from all these cues.