Flying standby can be a very frustrating experience. You have to sit around in the airport and wait, hoping that someone doesn't show up for a flight going to your destination. Dressing appropriately will make the endless waiting more bearable.
Wear business attire. If you are flying standby as a representative of the airline, the dress code is very strict. Men have to wear a complete suit. Women have to wear an outfit that is suitable for a day in court. Clothes that are revealing would be a bad choice.
Pick comfortable shoes. Even if you spend most of your time sitting, tight or uncomfortable shoes can make you miserable.
Choose a professional-looking bag that complements your outfit. Keep in mind that when you fly standby, you should have only one carry on bag. You will usually be unable to check a bag since you aren't sure on what flight, if any, you will travel.
Dress appropriately. Your clothes should be comfortable, neat and clean. Airlines can refuse to let you fly standby if a representative feels that your clothes are inappropriate. Nice jeans and a polo shirt are good choices. Revealing clothing will most likely get you turned away.
Add layers. Even if it is warm outside, the airport may be cool. Wearing pants and adding a light jacket to your outfit may make your wait more comfortable.
Choose the right shoes. Your feet may swell some while you are waiting. Keep this in mind when you decide what shoes you are going to wear.
Bring a bag that will qualify as carry-on luggage. Make sure that you have an extra outfit appropriate for flying so you can freshen up and change your clothes if you have to wait a long time for a standby flight.