You're already on the best site for information (shameless plug).
I did, however, forget to give you perhaps the best piece of advice. Customer service. Remember, there are some customers you can't please, so the best thing you can do is to grin and try your best.
Now, one of the little tricks I would do, is every so often, an aircraft regular customer would come in. During the week, I would use a notepad, and jot down questions to ask. I don't have the notepad anymore (lost it, unfortunately), but I referred to it constantly. It also had various other little tricks and tips...
I was able to answer pretty much any question an entry level flyer would have, and if I didn't have the answer, I would take down their number and give them a call with the answer as soon as I could. I would also give them the phone numbers of the local flying clubs, if they asked.
Anyways, every time he came in, I made it my best effort to learn as much as I could from him. By learning as much as I could from him, I was able to improve the service for others. This was key, as I was the only one of three employees (one being the manager) to make such an effort.
The other employee was a strict racing-level-only type. He wouldn't even take the time to be friendly with the customers' children (we also sold Learning Curve products, like Thomas the Tank engine and such, complete with a full display). Remember, the nicer you are, the more likely people are to come back.
Perhaps a bit long winded...heh.