Recently I read that when people are happy they tend to spend more.  All the more reason to ensure that when your customer walks in your door, they either stay happy, or become happy, personally I'm always happy when I'm shopping.  This can be accomplished by your merchandise mix, pricing and staff. 

Regarding merchandise, staying true to your brand is key.  Your customers shop your store because they know the type of product you carry, the quality and the overall assortment.  They are drawn to your store because what it has to offer coincides with their needs or desires.

Pricing is also important.  I've never forgotten walking into one of my local stores to buy some hand towels for my bathroom when I first moved into town.  X Dollars later, I walked out very disturbed.  The towels were so overpriced.  I bought them anyway because I was rushed, but believe me I didn't plan on returning to that store anytime soon.

Finally, how your staff interacts with your customers sets the entire tone for their shopping experience and can be the catalyst for a sale and a loyal customer who will come back.  Using the same store above, and by the way they are no longer in business; I did again attempt to shop their store because I loved their product assortment.  However, on this particular visit, the staff all but ignored me as I perused the shop and when I did ask questions, were totally un-engaging or better put unhelpful.  In my book, two times and you're out. 

So they lost what could have potentially been a great customer over the years, as I love to support my local retailers, because they had no concept of what or how to make(s) me happy.