Everyone should have front and rear lights (this includes joggers who increasingly use head lamps). Lights are measured in lumens; but don’t assume that the brightest light is the best light. Bright lights are good for dark trails but provide high contrast between what is lit and what is not - making it hard to see outside of the beam of light. I ride with two AA powered LED headlights that help define me as a bike and provide sufficient light on an urban trail. Strobe or flashing lights are commonly used for safety to ensure that bicycles are seen by cars. But strobe lights should not be used on trails where they blind oncoming bicycle traffic. Please set your lights to solid, and point them down at the ground in front of you (not into oncoming traffic's eyes). If you ride with strong lights, consider dimming or placing your hand over the light in the presence of oncoming traffic.
Be visible from the sides as well. Side visibility can be provided by reflectors, spoke lights, and ankle lights. Research has found that one of the strongest indicators to a car that what is in front of them is a bicycle is ankle lights or reflectors. The circular motion of the ankle is an immediate tell of peddling. There are also fun computer-enhanced spoke lights that turn your wheels into electronic art.
How good are your reflectors? Here is a simple test: take your bike out at night and take a flash photo. Any reflector on your bike should light up in the photo, showing you what you would look like in the headlights of a car. Of course I have a rear reflector, but I also have reflectors in my tire sidewalls. Capital Bikeshare bikes have these and they are brilliant. I also place reflector stickers on my helmet.
Finally, your high-visibility clothes aren’t worth anything at night. Research has shown that once the sun goes down, hi-viz is as dark as any other part of your clothes. Use lights and reflectors for visibility after dark.