I worked with a bike shop for just short of two years. Most of your customers are going to be super easy to deal with and talk to. The ones to watch for are those have have truly studied what they are researching and know more about the product you are selling than you do. I think the hardest single question I can think of being asked was "Why Specialized over (insert brand)".
IMO, if your store offers the training materials and such that ours did...I can't recall the name it was like Specialized tech school or some such....take advantage of it. Study it hard. In down times go through your sales brochures, take them home and look over them for each of the bikes offered for the active year and a model or two back can be helpful as well.
My single favorite thing about working there was being on hand, working, before all the group rides. I participated in all of them I could keep up with. Got me in arguably the best shape of my life.