Bellamy - you have him lay his head in your lap or on your chest and you run your hands through his hair until he falls asleep
Finn - you take his hand and lead him to the waterfall, and there you sit next to him and talk to him about his feelings
Lincoln - you sing him your favorite songs from when you lived in the ark, and you also tell him stories from your childhood
Jasper - you read books to him that you found in the bunker. He almost always falls asleep when you read to him
Monty - you take him to a place where you can be alone and you hold him and let him drain all his thoughts, and then you tell him jokes to make him laugh