Reputation and referrals are my lifeblood. I have been giving things away for 15 years - mostly information, insight, tips, etc. I have contacts who ask me for career advice all the time, even when not looking for jobs, and I always take the call and try to provide honest advice. When those people are asked who to use for search, they send business my way.
I now do very little marketing to new clients or candidates - I post some jobs on my site, but very little advertising and very few cold calls. The value of acquiring a set of very specific and useful information (market rates, info on companies, etc.) and providing that to your network when asked is rewarded down the road.