Probably the best course of action is to make sure naptime is at the same time every day. Play soothing music like that from the Lullaby CD on the list. Make this a habit so your child’s brain learns to expect to go to sleep at this time and to this music. This is the routine. If you are someplace else and you don’t have the CD with you, sing the songs to him. You are repeating the routine every day so your child’s brain learns when it’s time to sleep.