Form a mental image of how far away it is. Practice with your mirrors until you become a good judge of distance. Even then, allow extra distance before you change lanes. It is a good idea to give a quick beep before passing anyone that may move into your lane. A parked car has someone in the driver's seat.
Someone is in the street , riding a bicycle or walking.
In an emergency, press the horn button loud and long. Be ready to stop or swerve away from the danger. Keep in mind that a motorcycle's horn isn't as loud as a car's, therefore, use it, but don't rely on it. Other strategies may be appropriate along with the horn. At night it is harder for you to see and be seen.