This is one of the few jobs I have not had in aviation; however, gate agents do not have an easy job and they have bad days like everyone else. They also deal with myriad A holes during the course of a day, which primarily involves paying PAX. That is especially why being nice is so important. I also know for a fact that ones dress, demeanor and countenance can make a big difference between getting on or not. Look sharp whenever possible and don't stink. When non reving, on off time, always wear descent clothes; a dress shirt and tie is not out of line by any stretch. I would often have my swim trunks on, under slacks, if headed to the beach. Additionally, most gate agents are not impressed with the fact that you/we are pilots; it might impress a cashier at the grocery store, but not likely a gate agent.