Word-of-mouth is definitely how I end up getting most my business, with my Mom2Mom group & events in second, and Facebook in third.
It's funny, I won free advertising on Google recently, and according to the analytics, I've not had one click via those ads. I think maybe we are all accustomed to tuning ads out. I still don't know if I will continue the adwords after my freebie time runs out. Depends on the end results.
Mom2Mom is great way for me to get myself and my business out there. I'm a member of a Mom2Mom group (they're all over the place!) and I help with design ideas, getting the word out, setting up, etc. I take my portable studio set up with me to the Mom2Mom events and offer mini photo shoots on the spot, hand out cards and flyers, answer questions, and book appointments. It's really inexpensive for me to reserve a spot at the event, and I get in touch with hundreds of parents! I also make the mini photo shoots really inexpensive, usually between 1 and 4 poses, offer them a printed photo (just with my printer i bring) or a CD with watermarked images for a few bucks extra, and a coupon for a future sitting. I really put the pressure on these customers to book a "real" appointment, and I often get them. Even just posting on my Mom2mom's Facebook group has gotten me customers.
That brings me to Facebook, which is kind of like word-of-mouth anyway. My friends like me, their friends like me, a friend of theirs sees my page and the photos I took of a friend and calls me for more info. It's just a bit quicker than my friend calling their friend who says their friend is looking for a photographer for their wedding. lol. I make no sense, do I?