Well, I recommend a rear view mirror so you can see the cars coming up behind you. You also have to keep in mind that in general people here do tend to give good advice, but everything depends on your geographic location and the cycling culture there. If there is a road where the cars are doing 45mph and there is no bike lane, you are going to be better off looking for an alternate route, even if it makes your trip longer. I mean you may have the 'legal' right to be on that road, but it's better to be alive than to be 'right'.

You have to remember that a bike can cut through parking lots, bypass one way streets, go through back alleys, ride down stairs, and generally go a lot of places where cars can't go. So keep this in mind during your route planning. You probably won't be able to plan everything perfectly the first time out. You will slowly 'optomize' your route as you gain experience on the roads. Even if you know the roads as a driver, riding a bike is different. To give yourself self confidence, you should have a decent set of lights at the very minimum. You can also add reflective tape to your bike and or clothing, and as I said, a mirror.

Having said that, the best thing to do is just to go out and ride. It's a mental barrier that you just have to sort of break through. I mean you can't learn how to swim entirely from reading a book. Eventually you have to jump in and sort of figure things out on your own. We've all done it, and you will too.