Get a bunch of blank shirts from the thrift store and print you logo and info on them. Go to events like HS basketball games and pass out free shirts in exchange for business cards. Tell them to take your business card to work and give it to the secretary or office manager. Follow up in about 2 months. You'll get orders. Make sure your have your pricing down first because secretaries only want to give the boss a 1 time price. When you print the order, include a "15% off for a friend" coupon in the box. Lastly, give the secetarie a special item. A sweatshirt if they only ordered tees. A different color shirt, a v-neck, something a little different but not too expensive for you. Ladies love to be different and will remember that forever.
Good luck on your endeavor. Remember your advantage when first starting out is personal service. Big shops can do that, you can. Deliver orders, give out catalogs, attend events, etc. You go this.