I had one friend whose personal rule of thumb was:
- did they come to my table to take my order?
- did they bring my food to my table?
- did they bus my table for me after?
If they did 2/3, then they got a tip.
If you're eating fast food, you don't have to tip, though they've been asking much more than usual lately.
If you're at a sit-down restaurant or having something delivered, tipping is standard.
15-20% is normal.
And it's more offensive to tip low than to not tip at all. A low tip means they did a bad job, no tip might just be a protest against tipping.
Yeah, tipping culture sucks. I prefer eating at places that deliberately tell you not to tip, but they are few and far between.