1. Print business cards.
2. Pass the word for your services at local veterinarians, groomers, upscale pet food stores, etc.
3. Have a Web site.
4. Email all of your friends, former colleagues and acquaintances and let them know you are starting a business.
5. Go to nearby apartment complexes and leave cards in the office (put fliers up on bulletin boards if they have those).
6. Put fliers up at grocery stores and other places that advertise community businesses.
7. If there is a free shopper’s weekly newspaper in your area, offer to write a column about walking dogs. (What to do when you encounter other dogs on leash and off; how to keep your dog from pulling on the leash; etc.)
What I look for in a dog walker is someone who is responsible (comes on time for appointments, etc.), someone who genuinely likes dogs (pets mine; talks to them).
Good luck. I wish you were in suburban Maryland, because I need a dog walker in a couple of weeks.