For example: if you’re out to dinner and somebody else is paying, DO NOT order the most expensive thing on the menu.
Tailor your clothes when you can.
Owning formal clothing is an important part of “adulting.” Whether you have to dress up for work every day or not, it's important to have a tailored suit or other dress up gear, because you'll never know when you need it. A job interview could happen seemingly out of nowhere, someone could get married, or you may even have to attend a company work event where you have to dress up.
If you’re out to dinner and somebody else is paying, DO NOT order the most expensive thing.
It's just rude to order a $100 filet mignon, when you're not paying for yourself. Even if the person treating is independently wealthy, it will still go a long way for you to not order the absolute most expensive thing on the menu. If the person paying wants to order for you, then it's totally fine that they order the most expensive thing. But, you should use discretion when someone invites you out.
Always offer to pay…even if you’re being treated.
While you shouldn't order the most expensive thing on the menu, you should always offer to pay because it makes you look good. You don't want to seem like a mooch and you also shouldn't always expect someone to pay for you. If they end up taking you up on your offer, that's fine. The person who offered to pay may have not been able to actually afford it, they may have just wanted to impress you.
Don’t criticize your friend’s S.O. if they’ve done nothing wrong.
Your friend's relationship typically isn't your business unless they ask your opinion or you see that they're being mistreated or abused. As a general rule, try not to pass judgement or trash talk someone's significant other, especially if you've never personally experienced them doing anything that would warrant criticism.