For regular commuting I really like having a rear-view mirror. The one I use attaches to my helmet, but other types attach to the handlebar or glasses. FYI, backpacks tend to obstruct helmet/glasses mounted mirrors.

Finally, I’d like to stress following the [legal] rules of the road. Korey’s urban cycling link above has great info for this. Commuting cyclists aren’t that common yet, so it is important that we follow the rules to be respectful and establish common expectations. Be prepared for motorists that aren’t looking for you and/or don’t know how to behave (like yielding to you when they have the right-of-way).

Thanks for the thorough and informative post, Korey!