You have to make them want to smile even on their bad day. Give them what they need, support and then they will want to buy something from you.

Well, what does the customer want? Well for one thing, for me to be nice to them,. Secondly they want an item? Where is it? I will find it for you. That is it

They want something just point out direction and give it to them with a smile.

What do they want? polite service and no crankiness with that order.