People use social media in order to get noticed. They want to post images, thoughts, and products that their followers will like and share. Why not help one of your customers shine by featuring them on your social accounts?
The next time someone is in your shop having a good time, and obviously about to buy something, ask them if you can feature them on social media. If they’re OK with that - which they almost certainly will be - take a few photos of them shopping, exploring your store, and then of them buying something.
Post the photos on Twitter and tell the story of your shopper’s experience - who they are, what they bought and why. Make sure you tag them in (you’ll need to ask them for their social accounts to do this).
Everyone loves being made to feel special. Asking to feature one shopper will ensure that they’ll retweet that experience to their friends and followers, thus expanding your reach, too.