Life is too short for black handbags, white bras and boring people.
If someone you know suffers a miscarriage, then acknowledge their loss. Loss of a pregnancy or the ability to have a baby is a true loss. Treat these the same way you would the loss of a person or pet.
Respect people’s beliefs in religion or politics. Do not respect those who try to inflict these beliefs onto you.
Listen to other people’s opinions (within reason). You may learn a new way of looking at things. If someone (or even yourself perhaps?) is hogging the conversation with their opinions, fake a headache and get out of there.
Rescue your friends when they are stuck with boring people, but do it with grace and aplomb.
Treat anyone who is too full of themselves with scepticism.
When someone you love dies, you will want to talk about them. That is ok. If your friend wants to do the same thing, then let them. No matter how many times you have heard the story.