You have to acclimatize him to the process, reassuring him, but following some specific steps.
- Make sure you're well-rested the first night because this will take some time and some timing
- Make sure room is VERY comfortable temperature-wise and the bed as well
- Spend a few minutes holding and cuddling baby with some "goodnight sounds, perhaps a specific song or two for the bedtime ritual
- Place the baby in the crib, say goodnight and leave the room. Be sure to close the door.
- Baby will cry
- Let him cry for 5 minutes, the enter the room, reassure the baby in calm voice and goodnight words, but do not pick up the child, gentle touch at most...then leave the room.
- Baby will cry
- Let him cry for 10 minutes before reentering the room and repeating the earlier bried reassurance ritual, again do not actually pick the child up
- Next wait 20 minutes before entering
- Next wait 40 minutes before entering
- Then an hour
We used this technique on both of our children. Our first made it through step 11 the first night before falling asleep...a total of 2 hours work. The second night she was asleep by step step 9. Our second child had similar results, but it was the 3rd night before she was settling in for the night after only 1 return trip in.
The key is to teach them that crying DOESN'T get them mom or dad's presence back and them picked up after dark, but mom and dad ARE still there reassuring and they have to expend a LOT of energy to get that extra limited reassurance. They will learn quickly the effort isn't worth the return and will go to sleep.
Good luck. Hard on the nerves, but works!