Without spewing venom from my mouth and brain, I'll do my best to not launch into a long-winded tirade.
Why can't people simply ask a question or favor without being mean-spirited, obnoxious, condescending or some combination of all three? Seriously. People, when you talk to someone, do it with respect and you'll be flabbergasted with how thoughtful and hmmm, what's the word I'm looking for...ummm, oh yeah, respectful your responses will be.
If you ask a favor from someone and they can't do it for whatever reason, don't then make it that person's problem and issue just because you're too damn lazy to do the task yourself.
If you are not someone's parent or supervisor, do not ask that person to do something out of "common courtesy." Do the courteous thing and not ask anything that is inappropriate, against the rules, none of your business or some combination of all three.
Regardless of who you happen to be sitting and chatting with at any given moment, it is impolite to answer your cell phone. Seriously, let the call go to voicemail or tell the caller that it is not a good time to chat. Why would a call be more important than a face-to-face conversation? Unless the caller is telling you he/she is dead and needs you to go pick up their body, there really isn't a good reason. The rule about having a conversation via text is still with the jury; I'll get back to you about that issue when the verdict is in.
Do not overindulge any children for whom you are legally responsible. Nieces, nephews, young cousins, godchildren and children of friends are ok to indulge, but don't overindulge those from whom you want/need respect. You need to be a parent/guardian to your kids, not their friend. There will be time enough to relate to one another when the kids are grown.
And last but not least, dress appropriately. Nothing looks sadder or uglier than a 40-ish year old person trying to dress like a teenager.