Go to your local Chamber of Commerce, get the demographics for your area and drilldown to the pockets of people that fit your need and where you believe you can add the most value to their lives. Connect with other women small business owners via your local Chamber. You may also find there are opportunities to have a referral program set up if you don’t already have it presently.
Social networking sites and creating your own web site can be done inexpensively. Create flyers and leave at health food stoers, exercise and sport retail stores, community bulletin boards, hair & nail salons, city & parks recreation facilities. Send out press releases to local radio, tv & newspapers & mags.
Word of mouth is the best & most effective. If your participants are getting good results they are going to tell their friends.
First and foremost you must overdeliver your services and produce results in your attendees so that they spread the word. They will become your walking-talking billboard for referrals. This is the best free marketing you can ask for.
Then there are many other ways to fill the spots:
Bring a friend day
Referral specials such as for every person you refer you will receive free classes
Online newsletters sent to your list with useful information to keep people hooked
Hope this helps