I usually don't tip, as I live in a country where people don't depend on the tip. And if they got a problem with that, they can take it up with management. I am not their employer. Also, I don't get extra money for simply doing my job as well.

But there are rare occasions, when I do. And that's if I see that someone has gone unexpected "extra" lenghts, which can not usually be expected from doing the job.

For example, in an italian restaurant my partner and I ordered some noodle dishes. We were there often, so we didn't expect anything unusual. However, that day, the waiter just brought us some Parmesan cheese with the advice it tastes better with it and we shouldn't be shy to ask for it. That was very forthcoming and justified a tip.

On another occasion, when my partner had a hospital stay, we ordered some pizza. We did it once or twice, as the treatment took several weeks. Usually I went down to the building entrance and received the order. One day, there was an awesome delivery guy who took it up on himself to bring it to us to the patient room. We were very impressed. I remember that my partner said we should shower him in money, haha. We certainly gave him a nice tip.

Should I tip them for not spitting in my food or not stumbling and throwing it all over my clothes?

In the US, yes. Tipping here is insane.

If I go to a restaurant I expect them to take my order, bring me the food and when I’m done bring me the check. That’s it.

I've been to a Michelin Star restaurant where a pair of waiters were constantly hovering over your table to clean it and refill drinks and offer provide conversation.

The chef comes by and makes a presentation of every dish (the bananas foster was practically a magic act, the way they assembled the meal and then light it on fire). The staff practically wingman for you, if you've got a date. Everyone is beautiful and charming.

But that was something like $300/person just for the table, with 20% gratuity as a fixed fee on the final bill.

There are lots of restaurants that don't charge through the nose for the meal but offer comparable service. Charming friendly waiters who weedle your favorite food and give excellent recommendations. Staff that sing or make clever jokes or entertain small children or share a cocktail with you at the table. I know a few high end restaurants in Houston that will try to pouch waiters from one another because they're friends with particularly wealthy regulars.

You see less of that now (at least in the states) because individual waiters are expected to cover more tables, turnover is more important than relationship building, and the quality of food has taken a real nosedive as we replace professional chefs with meals made in microwaves.

Now a tip is much more like a Coperto - a cover charge for seating - than gratuity for exceptional service.

For me it usually about timeliness (I don't know if that's a word but it makes sense to me) and if our drinks a nearing empty they ask if we would like another rather than having to spend five mins trying to flag some one done.

Simply doing the job quickly and professionally which for me makes my meal a little bit better. Also this is much more achievable for the staff if the restaurant has enough staff.

My tip heavily depends on how full my water glass is kept and how long my dishes sit in front of me before they're cleared.

I don't need chit chat or being flirted with, I just need my meal in a prompt and courteous manner, that's worthy of 15-20% IMO.

Friendly, prompt with explanations for delays and either a remedy or some form of alleviation of the disappointment, good recommendations/feedback on food, etc. a big one for me personally is coming over only when you notice something is needed (drink low, people looking around, etc )

I'll tip if someone does those kinds of things as it's going above the basics I normally require

Good service is anything outside what you just said. Did you need to ask for any changes/ substitutions? Did you have an allergy they had to accommodate? Are you on a rush and they brought it out quickly for you? Are you splitting the bill? Are there children in your party? Did anyone leave a mess or did a drink spill? Were they extra helpful with recommendations? All these merit a tip. If they do exactly as you said and you were an easy customer, no tip needed (assuming you're in a country where tipping isn't customary)