First, give your baby a warm bath. No water play, just soothing bathing in warm water with a fragrant, gentle soap. Dry in a warm towel. Be deliberate, soothing and slow during the whole process. Younger infants enjoy being wrapped very tightly in a blanket for sleeping, so tightly that movement is difficult.
Most babies enjoy some type of rocking or vibration when trying to doze off.
Try the old standby, a rocking chair, or maybe a short drive in the car. Another thing I found quite effective was placing my babies on a bed made of comforters atop my clothes dryer, and turning it on. The gentle hum and vibration of the dryer had them sleeping in no time. And, I guess it should go without saying, make sure your baby is not hungry when bedtime is near. All of us sleep better with a full tummy.