Word-of-mouth advertising is often the most effective way of spreading the word on a sewing business. You do a good job for one client and the word spreads.
It will be slow at first, but once you get going, you will begin to get repeat work and referrals.
You can also leave your business cards or flyers in fabric shops, beauty salons, grocery stores, resource centres, etc.
Contact charity organisations and lend your sewing talents to charitable events. Get in touch with local theatre groups that may require your services for any costumes or set designs. By attending craft fairs you will be able to network and meet potential clients.
Establish partnership arrangements with cleaners in your neighbourhood. In the past, most cleaners kept an on-staff seamstress or tailor, but nowadays they outsource this task to sewing services.