How do you build your business, whether it be photography or anything else?
It's just a matter of "getting your name out there" and marketing your product! Easier said then done, as I continually find out. One of my mentors, John Shaw, once said that when you're in the field shooting, you're spending money, and when you're in the office working, you're making money. I've tried to take that to heart.
Networking is probably more useful in pulling in business than anything. But most people don't understand what networking really means. It's not approaching a group handing out your business cards and going around to everyone saying "buy my product - buy my product". You need to work on establishing relationships with people, learning their needs and offering value to them. I try to freely share things I've learned - even with my competitors. Hopefully, by adding value to the community at large, it will "pay back" eventually. Almost every job I've been offered is one in which I've established a relationship with the buyer.
Then there's that whole social media marketing thing. SMM marketing guru, Kevin Knebl, says that people tend to do business with those they "know, like and trust". While he feels that SMM may be just a momentary fad, he believes strongly that if you simply follow the teachings of Dale Carnegie, in "How to Win Friends & Influence People" (which I'm reading now), you'll outperform the majority of business people in whatever field you're in.
Hope this helps and good luck!