First, don't ever walk into the shop expecting to get business done.
Make an appointment. Shop owners are very busy, and consider it rude and inconsiderate to just walk in there expecting to meet with them about your products.
Ask to see them, leave a business card, and try to set up an appointment.
Then when you come back go back to all that nice stuff you started with.
For more help/tips check out these threads:
retailers related topics at T-Shirt Forums