Driving to avoid collisions in spite of the actions of less careful drivers is defensive driving.
Anticipation is one of the most important qualities in a professional driver. Space and time are your best friends if you keep lots of each on hand.
Anticipate trouble ahead. Assume the worst conditions and make allowances for every possible error. Keep your distance from the vehicle in front by using the two-second rule. When you see the car ahead approach a checkpoint, like a rod sign or hydro pole, count for two second. That's at least how long it should take you to reach the same checkpoint. You should never drive with less that 2 seconds and many conditions require more distance.
In conditions of poor visibility or traction, or if your vehicle is heavily loaded or you are feeling a little "under the weather" increase the distance between you and the vehicle ahead.
Make sure other drivers can see you... particularly at intersections. Don't hesitate to use your horn or headlights to establish eye contact. Position your vehicle clearly so other road users know what you plan to do next. Be predictable.
Use your headlights night and DAY.
Make sure your tires and windshield wipers are in good condition and your car has regular mechanical check ups.