Once I purchased my helmet, the next step was to increase my visibility on the road: a driver is less likely to hit me if they can see me : ) This is the head light and tail light I purchased from a local bike shop. I have used both of the lights for a few months now and I love them. Rain or shine they have given me no problems. Whatever light you decide to purchase, be sure they are placed somewhere that is visible to motorist. Also, be sure to keep them on the "blink setting," this will make you significantly more visible to motorists.
On this same note, it is important to increase visibility for day time commutes. Lights are great at night, but in the day increased visibility means bright clothing. Whenever possible, wearing bright colors, or reflective materials, will make you more visible on the road.