I agree with doing some test rides. Ride a bit after work, and a longer ride in the evenings. You don't want to be exhausted by the time you get to work.

+1 on the rack and panniers.

+1 on bright clothing, being visible will make you safer. I can't imagine riding without helmet, but it's up to you. I always ride in cycling glasses, helps with not getting bugs, dust in the eyes.

I find mirror very useful, they're not expensive to get.

Find out what are the rules of the road for bikes where you are. For example if you are required to wear a helmet, have a bell etc.
Have a look here, this is from where I live, but it may help: http://www.toronto.ca/cycling/safety/car-bike.htm

Ride close to the curb, but not so close that you have to go around drainage crate or debris. Try riding in straight line, rather than weaving in and out, being predictable to drivers makes you safer.

Make sure to watch for parked cars, ride far away to clear the opened door.

Pretty much follow the rules of the road, stop on red lights, stop signs, don't cut off cars and other cyclists (even though you'll see other cyclists do it....).

Have fun! If you can find a route away from major roads, you will enjoy yourself more.