-Click on the baby and select "Feed", "Feed", "Play", "Play", "Sing", "Sing". Note: It always has to end with "Sing".
-When your baby cries, click it select "Feed", "Play", "Sing", "Play". If you have The Sims Makin' Magic, you can buy the Skeleton Maid, then go to "Miscellaneous", then buy the gray coffin that stands up (named "Bag O Bones" Skeleton Closet). Keep the coffin close to the baby. When the baby cries, just knock on the coffin.