Best advice would be to take a MSF course if you haven't already.
My own personal advice....ride like you are invisible. Meaning always anticipate that a car sitting at a stoplight is going to pull out in front of you. Pick out "emergency" lanes ahead of time. That way if something does happen you already know in your mind the options of where to go. When sitting at a stop light leave the bike in gear and keep checking your mirrors for cars coming up behind you. If it looks like they aren't going to stop then all you have to do is hit the gas instead of trying to hurry and drop it into gear, then taking off.
Find a empty parking lot, or no-traffic road, and practice emergency braking. Get up to different speeds and pick a marker, then stop as quick as possible. Remember 70% of your braking power comes from the front end, but it's easy to lock up the rear and that's a big no-no. I'm not saying not to use it cause you'll want that extra 30%, but get used to the limits of the pedal so that you get maximum braking without locking the wheels up. If it happens, remember not to instantly let up off the pedal. If the tire breaks free from traction it can quickly get grip again and throw you for a spill.
I second Steel's comments. Check the air pressure in your tires often, and do the routine maintenance. My last recommendation is GEAR GEAR GEAR! Check out a site like Newenough.com for some great pricing on gear. You don't have to spend a fortune to get some basic protection.
Riding is one of the greatest things I've ever experienced, so don't be dismayed about all the things you need to do to help keep you safe. Welcome to the biking world and best wishes and safe riding!