Just throwing it out there that I own www.simplyappointments.com
My question to you is how large is your city? Sometimes people try and promote too large when customers will no do the travelling to get to you.
Google/Facebook allow you to specify your target market, age, location, and much more.
Word of mouth in your business I think is king though. Make sure your current customers are super happy and let them know you want more customers.
And yes, being able to book appointments online is pretty damn important. for me anyways.
Hope this helps you some.