The breeding isn't the hard part. Clownfish are pretty much nymphomanics and a mating pair will produce eggs every few weeks. The difficulty begins when trying to raise the fry. They need rotifers and cocepods, which need phytoplankton. The book Ski mentioned is widely regarded as the best book on Clownfishes and I've seen it mentioned on many forums. I will have to pick up a copy if I can find it.
Having a seperate refugium tank, solely for rotifer and pod breeding and growing your own phytoplankton culture will greatly aid you in doing this, I would imagine. Planning and preperation are definitely the key.