Your shirts or apparel first off must be original. The message, the design, everything has to be original. The one thing teespring purchasers hate, is to see shirts that look like other popular, already existing lines of tees. Your message must also be attention grabbing, unique, funny and interesting. The purchasers must feel like they're buying a shirt from a friend or good buddy. Not a corporation. As far as campaigns are concerned, blasting your apparel on social media works well. Just make sure to name all of your accounts after your shirt or shirt-line brand name.