Buckling up is the easiest thing to do. According to edgarsnyder.com, seat belts reduce the risk of a fatal accident by 45%. There is literally no reason to not wear a seat belt. It takes 3 seconds to put on and can save your life. I will never understand people who do not buckle up.
Another easy thing to do is simply stay off your phone. According to distraction.gov, over 3,000 people were killed in an accident caused by distracted driving. We've all messed with our phones while driving at one point or another, but it really is important to just put it down. Anything you are doing at the time can wait. Sometimes I even need to remind myself these things, but it really is a good idea and makes sense. It can be tempting to quickly respond to a text, but it is never worth your life.
Overall, staying safe while driving is all about common sense and being smart. Staying focused on the road, buckling up, and doing the little things to make sure you are safe are the easy things you can do to make your most life threatening part of your day safer.