Wearing high visibility clothing means that you will be seen when your riding your bike.  Wear fluorescent or bright clothing in the daylight.  When riding at night or in poor light, always wear something reflective.

Make sure that you have clean and visible reflectors on your bike.   It's actually against the law to ride a bike without a rear reflector.  Also, always use lights after dark or in poor weather conditions, they will help you to see your way and others to see you!