What should I be looking for when buying reflective lights for night riding?
Most reflective tapes are quite suitable. I've had good luck with 3M and Avery brands in general, but you need to strike a balance between cost and effectiveness. For example, SOLAS (safety of life at sea) tape is what is used on rescue buoys, life rafts, life vests... it is fantastically reflective and similarly expensive. 

Other tapes have a finer surface, but still reflect very well. I would recommend only getting white tape as it is the most visible. In terms of placement, here are some ideas:


On the inside of your rims between the spokes. You'll have to cut individual strips that do not overlap the braking surface. (This is similar to Velocity's reflective rim coating except that it costs much less and you don't have to build a wheel around it.) Even better would be to cover one half of the rim so that when it rotates the effect seems to blink.
On the backs and fronts of your seat stays and fork legs.
On the backs and fronts of your crank arms to bring attention to your pedaling motion.
On pedals or toe clips for the same reason.
Your helmet and other accessories so you're visible off the bike as well.


Clean everything with alcohol or some other solvent (especially your rims) to help the tape stick. In my experience, you shouldn't expect to get the tape off so be confident about the placement.

Visibility is a great feature for night riding, but don't skimp on your lights! A bright headlight is an absolute must for any serious night riding as well as two taillights (one as a back up in case your primary goes dead.) Dynamo lighting is a smart investment if you're riding at night very frequently (but you'd still want to use a backup taillight.)