Northern hemisphere days are getting shorter, darkness is coming sooner. For most of my readers, Daylight Savings or Summer Time will end soon. Whether you bike on the road or trail for recreation or transportation, that means lighting to extend your biking hours.
Cory at Making It Easier has a night riding primer. While he focuses on trail riding, he introduces the bare basics of lighting systems for bicycle use.
I'm currently using "be seen" lighting on my bikes for my twilight and after dark riding, but after Daylight Savings Time ends at the end of October I'll switch to my 12V 20W helmet light. In heavy traffic during the evening commute, I've discovered it takes more wattage to be seen than in light traffic.