This could likely be an infinite series added to long after I’m dead and cremated.
But here’s one of the fundamentals:
Don’t have headphones? Then never, and I mean NEVER, have your electronic device on anything but mute. There’s so totally no excuse for forcing anyone to listen to your music, your game’s super-annoying sounds, both sides of your Skype conversation, etc. In fact, I would go so far as to say if you are in public and you end up in a messaging conversation with someone —and so you are receiving a stream of steady alerts about their incoming messages—you should, after the first or second alert, put your phone on mute. Basically, your phone should always be on mute except when it might cause you to miss information. And if you don’t for some reason have headphones? Then no, you can’t watch that YouTube video, Vine (ha ha #RIPvine), or super-important Instagram story with the sound on.
Oh you’re a douchebag? What, you’re not? Then no!