As long as you know your shit you will always have something to say back to the asshole customer. Be confident in your knowledge. I think managers are pussies usually.
When I worked at Sports Authority for 5 months I sold shoes. Do you know how pissed off people get about shoes? Wow. And then they all want a damn custom order. So I always had to go to the back of the huge store and make like 5 phone calls to different stores around the country and ask if they had a product, then once I found one I had to get the persons address and do a manual copy of their credit card, and fill out a report. Then my managers got mad because shit got stolen since nobody was watching footwear. Then customers got mad because they couldn't get any help and the shoes were out of order, or I didnt have their size and couldn't get it for them, theres no more in the back, they got mad because my name was Rick, and they didn't like my shoes, they were mad because I was born in the first place, all over some damn 39 dollar convereses. Fuck... I hated retail, but it was so fun because of the people I worked with. But it sucked when we were busy, or if I worked alone. Which was like 80 percent of the time.