You don't technically have too by law but if you decide not too... you should know the server will likely be irate to the point of secretly wishing you dead. I highly recommend leaving a tip or just don't eat out. Order the food for take out and just pick it up at the counter, but do not expect someone to be super happy that they just served you for basically nothing.

You need to tip places where you sit down to eat with waiters, yes. ~20% of the subtotal before tax. Don't be intimidated by those little tablets asking for a tip for places where there is no table service, there is usually a no tip button. Just relax and don't hit a button right away. They make it a little smaller.

no it's not required but I can afford to tip so I do and that makes me better than people who don't ;)

It depends on the business. My advise would to look around you to see what everyone else is doing.

You have to tip 20% of the bill minimum. You can round-up only from there.

It's considered very rude to tip less than 20% because in the US, most service workers are legally allowed to be paid less than the minimum wage ($2 or $3 per hour is not uncommon).

You should give $1 to a bartender for every drink you order. If it's an expensive city, you should give $2 per drink.

You should take a look at https://en.m.wikipedia.org/wiki/List_of_US_states_by_minimum_wage and see what the minimum wage is in the state you are visiting. The minimum wage where I am is one of the highest in the nation so I don’t tip anymore.

Edit: I am aware many states have below federal minimum for tipped employees. My point was if they’re visiting one of the states with a high minimum wage, they should forgo tipping. Nobody below bothered to link it, but here's the minimum wage page for tipped employees: https://www.dol.gov/agencies/whd/state/minimum-wage/tipped. It's worth noting that even in the states that can pay tipped employee as little as $2.13/hr, the employees never actually make less than the federal minimum of $7.25/hr because the employer has to make up the difference if the employee doesn't make enough in tips, not that $7.25/hr is even remotely a livable wage in 2023...

Regardless, tipping is an inherently flawed system, and it's not the responsibility of the consumer to pay specifically the server a living wage while everyone in the kitchen suffers (I would know, I've been there). If you're not happy with the wage laws in your state, get involved in politics and exercise your right to vote to do something about it.

I tried not tipping on a US visit. You can get away with it, but people will be angry.

It's just a silly local custom you have to put up with when in America.

When in Rome…