In this thread we impart little nuggets of wisdom we've come to realise and learn as we've grown older. This could be anything from how to behave on the net, to how to talk to your boss, to how to treat shop assistants.
They might seem really obvious to you, but I still think it'd be nice to hear other people's. I'm sure we all aspire to become better human beings so let's help each other along the way!
I'll get the ball rolling!
Memorising details
When you speak to someone, make sure that as well as remembering their name, you remember something that is currently going on in their life or will soon. This could be a holiday they have planned, or job applications, or a difficult essay they're working on. The next time you see them, ask them how it went or if they've finished it yet. It makes people realise you are interested in them and enjoy their company. They'll do the same in return.
Confirming attendance
If you aren't sure if you're going to be able to attend an event, it's better to say you're unable to come (and then turn up at the last minute), than to say you can attend (and then bail out at the last minute).
Disappointment vs Arguments
If someone has done something to you, or something you disapprove of, then it is far more effective to show your utter disappointment in them/it than to tell them off for it. They can't become defensive to disappointment as it's your opinion and will remember the incident. Heated arguments are rarely beneficial to anyone.
(those might seem really obvious and stupid to people, so if so then give us some of your own!)