In an ideal world, common decency and politeness would be natural for people. In this ideal world, we wouldn't need to post obvious rules in airplanes and restaurants instructing people to be hygienic and aware of others, but alas - we live in a wild world full of people living on their own terms.
Still, we all have a choice on how to conduct ourselves, and setting a good example by being mindful of others can never hurt. Sometimes, it can be helpful to glean the unwritten rules of other people to have a better scope of how the strangers we pass on the street process the world.
Don't watch loud videos on your phone at a restaurant. Can't believe this isn't common courtesy anymore.
If I show you a picture on my phone, don't go swiping sideways.
Let us get off the lift/train before you try to barge on ffs.