The primary consideration is obviously safety. Riding a bike on the road is pretty safe, so don't let what I'm about to say scare you. These are just some general tips.
1. Get comfortable riding with traffic. It's unavoidable, and your riding is the most important factor in your safety. You need to ride in a way that is predictable. Follow traffic laws and clearly signal any time you are going to turn, change lanes or even change positions within a lane.
2. Find a safe route. You probably won't want to bike the same route you would drive. Residential streets with minimal/no traffic are preferable even to busier streets with bike-specific infrastructure. An example I like to give is that there's a place on my commute where I can choose between Main Street with a bike lane or Meadow Lane with no bike infrastructure. Meadow Lane is way better. If you have to ride with traffic (and you will) look for roads with a bike lane or at least a wide shoulder.
3. Any place that you don't feel comfortable sharing the lane with a car move to the center of the lane. If you give cars just enough room to squeeze past, they'll do it. You are responsible for your own safety and when you don't think a car can safely pass you you should communicate that by your position in the lane.
4. Don't let yourself think that you know what drivers are going to do. It's a big mistake to think that a driver has seen you and will not cross your path. Ride defensively. Imagine that you are invisible, because it isn't far from the truth. Also remember that it is very common for drivers to misjudge your speed. They tend to behave as if you are moving at the pace of a pedestrian.
5. Be very careful riding past driveways and entrances to parking lots. Avoid roads that go past a lot of strip malls. Drivers go in and out of parking lots without looking for bikes and usually without giving any advance notification of their intentions. Most drivers seem to think a turn signal is used to indicate that they are in the process of turning, not that they plan to turn soon. There's no reason to believe that a car not using a turn signal isn't about to turn.
Apart from safety, be prepared to fix a flat.