I recently bought this book and am half way thought it. It seems be an excellent source for this type of information...
http://www.amazon.com/Clownfishes-Jo.../dp/1890087041
From what I've read so far, they will decide in the first few months who is going to win the prize of being the female - then they'll eventually begin sharing a nighttime area together... I haven't gotten to the part yet that tells me what age they start spawning! But I would really recommend the book - it's great! She gives all the detailed information on what you need to breed them...