Cycling shorts have a chamois insert to provide padding between you and your bike seat. Although those "shorty" shorts may look cute, you should opt for the longer mid-to-full-thigh length shorts to prevent inner-thigh chafing. You should never wear underwear along with the shorts -- the materials used in pads today are designed to wick moisture, breathe and prevent the propagation of bacteria. As such, they are more sanitary than your underwear. The whole purpose of the bike (chamois) pad is to prevent chafing. In order to work, the shorts must fit your body like a second skin. Having a layer of clothing between your body and your shorts will prevent the shorts from working the way they should, and will increase your chances of experiencing chafing and sores where the underwear sits against your body.
When cycling, dress in clothing that is snug-fitting. Loose pants can catch in your bike chain or wheel. They can also rub your skin and cause irritation. Accomplished cyclists often opt for fitted stretch clothing to cut down on wind resistance. If you have room in a backpack or saddlebag, you may want to bring a windbreaker along in case the temperature is cool.
The technical fabric of jerseys pulls moisture off your skin to keep you dry. Cycling jerseys should not absorb moisture; they do not get heavy with perspiration. On cold days, cotton will absorb water and hold it next to your skin, chilling you. Do not wear cotton cycling jerseys, especially on cold days. Look for a jersey with pockets in the back to hold energy bars, keys, phone, etc. Choose Lycra/coolXtreme™ combinations or other technical fabric designed to wick moisture away from your skin.
Always wear close-toed shoes to prevent foot injuries. Never wear sandals or bicycle barefoot. If you are going to do a lot of cycling, you may want to look into some specialized cycling shoes. These are lightweight, low profile and made to fit into pedal cages or clip directly to specially made pedals. Clipless pedals, those designed to accept cleats, are the best because they provide the most efficient pedal stroke. Stiff soles of cycling shoes allow better power transmission to pedals. Mesh vents allow air to circulate around feet, keeping them dry.
Helmets should fit on top of the head, not tipped backward. Always wear a helmet while riding a bike, no matter how short the trip! After a crash or impact on your helmet, replace it immediately.
You should always wear glasses (sunglasses) while cycling to protect your eyes from wind, dirt, debris and the sun. Your front wheel or someone else's rear wheel can shoot glass or dirt at your face. Keep perspiration out of your glasses with a thin headband around your forehead. Another tip: If you do not have a headband, fold and place a two-ply paper towel in the crown of your helmet before putting on your helmet. This will absorb a lot of dripping sweat from your forehead and prevent it from reaching your eyes.
Gloves provide padding to help increase comfort and relieve numbness while riding. Protect your hands in the event of a fall with cycling specific gloves. Cycling tights keep your legs warm and out of the wind when it is cold. Muscles function better when they are warm and protected from the elements. Full-length leg warmers, which can be removed during a ride, are also a good idea.