I remember from my first visits to Radio Shack in the 70s, and they had a system at the cash register of getting your name and address every time. Then they would set you up for a regular mailing of their sale catalogs. It was a great system except for one thing: every time you went in, they wanted you to fill out another form.
Safeway supermarkets took that a step further and in the 80s came out with the Safeway Club Card. You fill out the form once, then you get a card and if you forget your card, they enter your phone number and there it is and you're in. The enticement is the discounts that only come from the club membership. They scan your card first so the cash register knows you get the club price. It was a bold experiment for a grocery store chain back then, but it is still in operation today and doing very well. In addition, other grocery companies have copied it along with many, many other companies.
Basically we are creating massive follow up opportunities to continue to market to our own customers! What a novel idea! It is just amazing how many businesses do not do this. It sure seems beneficial to every business I can think of. The real bonus in today's market is the email address and being able to market to your customers and follow up with your customers with the click of the mouse and have the cost be next to zero dollars. Direct mail is not cost effective anymore. Matter of fact, in comparison, it is downright expensive.
I took that Radio Shack idea and used it in my first business in 1979 and it was very helpful. This was long before email became a reality, but we sent direct mail flyers and had great success.
Build a database of your clients and prospects that come into your store. Get at least the name and email and more if you can get it smoothly. This will benefit your business in many ways.