Seat belts 4 points

One of the easiest, cheapest, and most effective ways to reduce risk in a general aviation airplane is to make sure it is equipped with adequate passenger restraints—seat belts and shoulder harnesses.
The FAA says the proper use of shoulder harnesses, in addition to seat belts, reduces major injuries in GA crashes by 88 percent and reduces fatalities by 20 percent. Wear your seat belt and shoulder harness on every flight. As a private or sport pilot and eligible to carry a passenger, you will want to ensure your right-seater knows how to fasten and quickly unfasten any belts and harnesses. Make it part of your passenger briefing.