Sir Bradley Wiggins echoes the same sentiment as I do, #1 item is Wear a Helmet!
Click here for the rest of the article. # 2 would be to always have a Blinking rear red light at or as near to driver seat level on the rider/bike! #3 would be to wear as bright of cycling wear/shirt/gloves as possible.
The Bikefriendlyatlanta kit is if not the brightest, one of the brightest out there! Get it here!