We get it! You want to ride your bike, but heavy traffic and seemingly careless drivers make you choose to use dreadfully crowded and slow public transit, pay for a cab, or even drive a car yourself.
Turns and stops. Does a driver want to turn or stop? Are their indicators on? Is he/she checking her mirrors? Is there someone in the passenger (or other) seat who wants to get out of the car?
Parked cars. Many times, bike lanes are aligned right next to parking spots on the side of the road. Unfortunately, this area is also the so-called door zone where extra caution is key. After all, a parked car may pull out on the road or a driver or passenger may open a door unexpectedly. In doubt, reduce your speed or give these cars extra space by moving to the center of the road — but, before you do so, make sure that nobody is about to pass you! It is also a good idea to pay attention to whether the car's engine is running, its lights or indicators are on; whether the driver seat is occupied, and whether the front wheels are turned into road. You don't necessarily have to focus on all these details all the time, but it is a good idea to train yourself to notice these things as they can help you evaluate how likely it is that a car will pull out or someone will open a door.
Traffic lights. Are traffic lights about to turn? Some people may want to catch the last moment of an orange light. Check before you cross an intersection, especially if your light just turned green. Clearly, do NOT run red lights!
Speed. Learn to judge the speed of all kinds of vehicles. Is a car too fast to stop before a light? Chances are, they will cross it. Will a runner or pedestrian try to cross the road? Is someone about to run a red light?
Communicate! As in many other aspects of life, communication is an important factor on the road. Knowing others' intentions helps us adjust and react accordingly. Sometimes you will have to decipher drivers' and pedestrians' next steps before they happen based on their behavior; other times you are lucky and they will let you know what they are about to do. Keep in mind, it is your responsibility (and in your best interest!) to communicate your intentions to others! This not only applies to turning and stopping, but also to making others aware of dangers.
Use hand signals. It is easy and takes minimal effort: Signal before you turn or move to the center of the road, to show what you will do. Point to the ground to make other cyclists aware of dangers such as potholes. Signal if you are about to stop. Also, let hesitant drivers behind you know when it is safe to pass you.
Make eye contact. A simple eye contact is often all it takes for another person to know what you want to do and vice versa. This applies to anyone you might encounter on a road: Drivers, pedestrians, other cyclists, etc.
Make yourself visible. Keep in mind that drivers might actually not be able to see you. Avoid the dead space of mirrors, the sides and backs of large vehicles such as buses and trucks, and make sure you and/or your bike wear lights in the dark.
Be courteous! Say thank you with a gentle nod of your head, or a (friendly) hand signal! Out on the road, you are an ambassador for cyclists and want to leave a good impression to encourage a friendly co-existence!
Be assertive! Sometimes you will have to be assertive and just claim your space on the road (e.g. changing lanes in busy city traffic). When you do so, (1) make sure you communicate your intention, (2) confirm that other traffic participants have enough space to react to what you are about to do (right speed? enough distance?), and (3) only then do your thing. As mentioned above, drivers are not out there to harm you. They want to protect your life and your bike as much as they want to protect their lives and their car.
Be Prepared! Regularly maintain your equipment. Having a working bicycle can prevent accidents as well. Lend special attention to your brakes, tires, and chain. Here's a good example for a maintenance schedule.
Abide the law! This should be an obvious one. Don't run lights, etc. You know the rules (if not, read this); you expect drivers to follow the rules. Follow them too! Again, when you are out on the road on your bike you represent all cyclists. Make sure to leave a good impression!
Josh Zisson, a Cambridge-based lawyer, created Bike Safe Boston, a great blog with many good resources about cycling in the city. Amongst other posts, we recommend you read the MA cyclist's bill of rights and the 10 commandments of city cycling. These posts will give you some general pointers (as the above) as well as information about what to do when you are unlucky enough to be involved in an accident (spoiler alert: Don't forget to get the driver's information!).
If you are riding in a group, some additional rules apply. We have compiled a safety policy document that we encourage everyone to read who leads or joins a ride with us.