Question

When you cross or enter traffic from a full stop, how much space should you allow on city streets? On the highway?

Answer 1

When stopped at any light or intersection, you should allow any vehicle approaching the equivalent of at least one city block before entering. Also check to see that no approaching vehicle is travelling at an excessive speed (moving ahead of the other traffic). Once you have made a right turn at an intersection, check your rear view mirror quickly. Sometimes you may have to speed up faster than you thought due to a vehicle approaching faster than you originally thought. 
If you stop behind other vehicle in traffic, you should stop so that you can see some road ahead of your vehicle as well as the rear tires of the vehicle ahead of you. This will prevent you from hitting the vehicle ahead of you if you are rear ended.....also check your rear view mirror whenever your foot goes onto the brake......if it is winter, this method will also help prevent you from skidding ......winter driving means you should come off the gas sooner, and brake early and gently and check that rear view mirror! 
All the best to you and your driving!