Marketing for the freelancer in any like of work is all about networking. Here are some ideas that I've found to work in my time as an outdoor instructor
You need to get to know the other people in the business. For instance if you want to get into wedding photography you need to know the wedding dress shops, florists and hotels that are involved in locally. Its recommendations from them that will bring in the work
Understand that when they recommend someone they are putting some of their reputation on the line too. If you do a bad job (in the customers eyes) then they will be tarnished with the same brush. If the customer thinks your great then they'll get some of the credit too.
You've got to prove your worth again and again, there is no way round it. Ask the photographers in the area if they need a hand. Be their lacky, help them out. If your good you could well get work through them when they are busy
Never poach clients from those you work for. The freelance scenes tend to put a lot of store in trust. Become trusted and you'll be allowed into the gang where often work is shared between folks when they are too busy
Websites, business cards, social networking and the like support all this not substitute it
Be an excellent photographer. Find opportunities to show this and build your reputation. Be the nicest, most helpful, most relaiable, most professional and mosty trustworthy guy in town and get out and about as much as possuible to build your reputation in this area too. Work for free a lot to start off with but understand that providing value for money is not about being cheap as time goes on
Word of mouth is everything