A properly fitted helmet is the most important piece of safety equipment, and you should wear it every time you ride, no matter how short the trip. According to the National Highway Traffic Safety Association, "A properly fitted bicycle helmet reduces the risk of head injury by as much as 85 percent and the risk of brain injury by as much as 88 percent."
Ride a bike that fits you. Make sure the seat height is adjusted so that you can pedal comfortably. Stand over the bike. There should be an inch or two between your body and the tube. Riding a bike that is too big is dangerous; you will not be able to control it properly and could swerve into traffic or other hazards.
Check to see that tires are properly inflated. Improperly inflated tires can make it more difficult to brake. It is also harder to steer the bicycle, and the tube can even roll right off the wheel. You are also more likely to get a flat if the tire is not fully inflated, which puts a damper on your bike trip pretty fast.
Test out the brakes before riding. You should be able to apply enough pressure to stop the bicycle quickly, without feeling like your hand muscles are working too hard. If the brake pads are worn down, it can be difficult to stop. You or your bicycle technician can adjust the brakes for you if the brakes are not performing to your needs.
Make sure that you are very visible to drivers to avoid collision. Reflectors and reflective clothing are important if you are riding at night, or in foggy, dim conditions. You can purchase jerseys that have reflectors on them, or buy reflector tape and modify your existing clothing.
Lights are another safety item to include for riding in the dark. A flashing light will call even more attention to the fact that you are on the road.
If you are wearing long pants, use a trouser clip on the right leg to keep the pants from tangling in the chain. Not only will this ruin your pants, it could cause you to lose control of the bicycle.
Gloves are a good idea to protect your hands in case of a fall. Many bicycle gloves also have padding on the palms, which can make for a much more comfortable ride. Sunglasses will keep your eyes clear of grit and protect them from wind.
Leave your music player at home. When riding your bicycle, it is important to use all your senses to be alert and safe. You need to be able to hear if a car is backing out of a driveway, or coming up behind you.