The best way is to give him a real-world project that will force him to program. Have him make a web site, or set up a web server from home so that his friends can log on over the internet directly to a computer that he controls.
Be aware, though, that it really takes a special mindset to not only enjoy programming but be good at it.
They need to really have a strong sense of order. Attention to detail is required. They need the ability to concentrate very hard and be able to flow chart behavior in their heads.
If they don't possess these skills, they'll find programming intolerable.
I love programming. But when I first started, I thought computers were only good for games. I thought programming was retarded. But by my senior year of college, I took on a project that required assembly level programming of a dsp chip, and that hooked me. I enjoyed the zen-like state I went into when I started programming, and I enjoyed putting code in order. I used to spend lots of time as a kid building snow forts and arranging the best location for my snowballs for a snow fight. It's the same sort of mental pattern I use when I program as well. Now I program at work and in my spare time. I love it.