There are things you should not say:
Never comment or ask a woman about her age or weight.
Never comment on how many kids someone has (or doesn’t have.) The size, timing, composition, etc of someone else’s family is not your business to weigh in on. You never know who is struggling with loss or infertility, etc. And if someone announces they are expecting their seventh kid, the only correct response is “Congratulations” “How are you feeling?” etc. Just like you would if it was their first. Never ask someone how much weight they lost. If they’ve lost weight, just say “You look wonderful/amazing/ fantastic, etc.” And of course never comment on anyone having gained weight. Just say “You look wonderful.” And never never never ask someone how much money they earn or how much money they have, or how much they owe or paid for something, etc. People’s finances are personal, and are just not any of your business.
IMPORTANT: If you borrow money from someone pay it back as soon as possible. In full. If you borrow an item, return it in excellent condition. I’d say if you borrow a car, return it with a full tank of gas but hopefully by the time you’re driving there won’t be any combustible engines. So return it fully charged!
Start “home economics” school with them. Laundry, cleaning, cooking, how to change a diaper, comfort a baby, soothe a toddler, what's involved in caring for pets, budgeting for food, keeping track of maintenance schedules for humans, pets, cars and machines. Engage with guests, be a good host, etc. Know when and how to tell someone to GTFO of the house (racist or misogynistic speech, etc.) Every kid needs to learn the art and science of home management. Look for and point out examples in books and movies of good home science skills.
Don’t have a clue? (Relationships / career / character, etc.) The solutions can be found in books. READ! Novels, biographies, history, religion, humor, politics, finance, sports, and whatever sparks your interests at the moment!) You’ll learn about the world, and you’ll learn about yourself. READ!!!! (or listen!)
Be discerning about your sources of information. Some red flags: Too good to be true. Get rich quick. Chosen race. Any race or group blamed for societal problems. Fear of change. Threats of real or metaphysical harm (I.e. $@!#%) or bribes with reward.
Have a yearly “review” right before school year. Raise allowance as appropriate. If they want more money, they’ll have to take on more responsibilities.
Take the family on periodic “spending fasts.”
As an exercise, go a day, a weekend or a week without spending any money. Make due with what you have.
Encourage participation. Tie in spending fasts with holidays, lent or in support of a cause.
Misquoting someone here: “It’s not about getting everything you want, it’s about giving everything you have.” Stuff will never satisfy. Pouring yourself into something heart and soul will.
***Manners!! *** Etiquette is the secret sauce. Everyone appreciates being treated with respect. Etiquette is the art and science of respecting others. It’s timeless and universal. Customs change, hence the need for constant study, but respect is always the foundation. In summary: Be nice. Start with yourself. Study etiquette. It will help you in every single interaction you have, social, professional, financial, everything. Manners apply to every human, in every interaction, even on the hard days. Hence, the need for practice.