During the day it is recommended to wear highly visible clothes (i.e. bright colors or reflective wear). Also make sure not to ride so close to the right of the lane, aside from weaving in & out of parked cars and avoiding hazards on the side of the road, motor vehicles will see you better if you "Claim the Lane".
At night visibility is in greater need; high visibility clothes aren't enough, it is highly recommended you have a front and rear blinking lights (steady lights may be missed or disregarded as part of the scenery by motorized vehicles).
Some External Reading
Standard Bike Safety
Riding with Traffic
PA Bike Laws
City of Warren Bike links
How Not to Get Hit by Cars
Wikipedia - Bicycle Commuting
Commuting 101
