My 8 month old son?

Start by doing the same routine every night. A bath is very calming. After his bath,put on his pajamas. Either give him a bottle or nurse him. This would also be the time to play some soothing music and read him a story. I highly recommend Goodnight Moon. Make sure it is a calm soothing story,not something too exciting. This is a good age to get him interested in books. After the story,rock him a bit,and then lie him down. It's nice to have one of those crib toys that play music and have lights. Wind that up and walk away. You need to do the same routine every night. When he cries and you go back to him,he is basically getting the idea that this is what works and what he should do. Eventually he will learn to self soothe and fall asleep. Just be patient and try to stick to the same routine every night. Good luck.