When you host events at your store, do you capture the contact information for customers that attend? One way to do so is by offering a door prize. Place a door prize sign-up form on each chair, or hand them to customers as they enter the store/venue. Gather the completed forms before the evening is over and draw for the prize that night.
If your event is a book-signing only where a large line forms, the store is often required to hand out signing guidelines. Add a door prize sign-up form to the bottom of the guidelines page and ask your printer to add a perforation. The customer can complete the form while standing in line and place it in the hopper on the way out.
Choose a door prize appropriate for your store. It could be a signed copy of a book, or perhaps a gift card to your store. Whatever you choose, the cost will pale in comparison to the value of the customer data.
Once you have the customer data, create a list in your email program for those attendees. Then when you host a similar event, you can select the specific customer lists you want to target.