I would say have him drink a gallon of milk everyday, (chocolate milk if he doesn't like regular milk) a few protein shakes every now and then throughout the day, and lots of cereal, oatmeal, steaks, chicken, bananas, bread, ect. It's all going to come down to the diet. Have him lift hard and heavy focusing on the core movements, most importantly: Squat, Deadlift, Bench, Rows, Pull-ups, and Dips. Keep making improvements in strength from week to week but also throw in some high volume every few workouts. Get him on some creatine.