(thoughts and reflections)
Second to lights on your bike, reflectors serve as an additional method of being seen at night and safer while night riding. In addition as backup to your lights, they enlarge the visual image to motor vehicles and when in the direct light of the vehicle headlights, they can be even brighter than the popular red flashing clip-on tail lights. Many night riders and commuters put reflective tape all over their bikes, and I am no exception. It is cheap insurance. And if you are hit while riding (stupid moves excepted) at night with high visibility, you will surely have the jury on your side in a legal case. [Little short story]
Reflector tape is available at many hardware, auto, and recreational stores. I have found that a better variety of tapes are available on the Internet. The above photo shows a few of the colors available.
For my bike helmet, fenders and panniers I have used the SOLAS white tape which comes in 2 inch wide 10 ft rolls. All which have curved surfaces, and in the case of panniers also needs to flex without peeling. The tape I use is 3M SOLAS approved (used mainly at sea on lifeboats, life vests and rafts) and has a rubber base that allows it to stretch to a limited degree on compound curved surfaces, like a spherical or saddle shape. It has a really tenacious backing and will not come loose. Other metallic (like the red tape on the helmet) and cloth reflector tapes only curve in one direction, like around a tube, and does not conform to curved helmet surfaces as well. All my panniers have extra SOLAS reflector tape on them. A reasonable source of SOLAS tape is http://www.identi-tape.com/solas.html
I also put the metallic colored reflective tape on the inside of my bike rims. A good source of this kind of tape is http://www.identi-tape.com/hi-intensity1.htm. If your rims are more or less flat in the inside (ie, not aero rims) the tape will be seen from the rear and the front, when viewed from a slight angle, as when being approached by a passing car. I use a blue/amber combination just to be different. Note that in many States is is illegal to put blue reflectors on the rear of a vehicle. I'm bending the law a little to my advantage.
A cheap and excellent reflector is available at many automotive stores as seen above. The oval reflector, sold in pairs for $1.50 to $2.00 has sticky double backed tape on the back. I peel of the sticky tape and fasten a metallic paper clip to the reflector using a medium nylon tie wrap. The tie wrap is not pulled tight, but is just loose enough so the reflector can hang (gravity) from the reflector. Note which clip is tied to the reflector. The photo shows the reflector face up.
These reflectors can be hung from any attachment on the rear of the bike. They should be clipped so they point directly to the rear and hang freely. The reflector has to point directly to the rear to be effective, it only has a +/- 20 degree angle of reflection.
The above three photos show the bike at night from the rear. On the left, with just tape reflectors illuminated from the rear, and flashing lights off (the upper Vista light has a reflective cover). In the middle, with the addition of dangling oval auto reflectors. On the right, the same with the flashing lights on steady. Notice the increased visibility due to the dangling reflectors. In addition the the dangle reflectors, the upper dual mirror mounts have white reflector tape on them. The two little white reflections, above the red light, are from reflective tape built into the bag. The amber reflections on the bottom are the pedal reflectors and amber rim tape.. The blue is also reflecting rim tape. When riding, the rotating pedal reflectors and rim tape are quite unique to a bicycle on the roadway.
For more information on bicycle headlights, chargers, mounting, and more, check this reference. You can also go the the Bike Forums and do a search on bike lights