Welcome abord slow driver.
Welcome to TAI.
Don't worry this is the very first question every driver has when he begins driving the car. I bet with experience you yourself will get the answer.
To get the basics clear, Firstly as per RTO norms one should maintain a minimum distance of 5 foot from the vehicle in front of you to avoid accidents. (Trust me this i learnt from a cop when a driver bumped his vehicle on mine from behind)
Try adjusting the height of ur seat, if not posible place small pillow on the seat for better visibility.
Some people install small metallic pointers on the co-passengers side on the bumpers to judge while driving.
This cannot be answered specifically as it can be best answered only by practice and driving the car. Park your car in your garage and from the drivers seat view the objects near the car. This will help you getting a rough idea on how much is the safe distance that should be left from the co-passengers side for other vehicles.
I also faced this question when i began driving and got it answered by practicing and judgement.