As a former server, I tip depending on the level of service I get in relation to how busy it is. I have left a few cents tip before. In my defense, it was REALLY BAD SERVICE and the restaurant was dead (as in my server only had me and my friend in their section and we couldn't get our server to get us refills and shit so really bad service). I did feel kind of bad about it as I know minimum wage sucks and you can't live off of it, however, I believe if you want a decent tip, you need to at least TRY to give decent service. I regularly go out to a restaurant once a month with a large group of friends. We all split our checks and we all tip. My regular order comes out to about $16.00. We usually get really good service. As I don't have a lot of money to spend I can't tip as much as I really want to and I feel bad. However, going by a 15% tip, I tip almost double what I should be tipping (hand server $20 tell them to keep the change). However, at that restaurant we also get REALLY good service too no matter how busy they are. Personally, had I the money, I'd do at least an $8 tip because our two servers we usually get deserve that for how hard they work and how great they are. That said, if I don't have money to order something and leave a tip (I've left tips on water before because that's all I ordered and felt bad that it was all I ordered so I left about the price of a soda which was all I had on me), I typically don't go out to a restaurant.
I judge others on how they tip as well. I've met people who boast proudly that they never tip because of how easy it is to be a server (at which I've interjected and put my personal experiences to them and some have actually changed their policy on tipping because some people are just ignorant and don't know better). My best tip I've ever gotten was from two guys who one ordered a double crown and coke and the other a double jack and coke. Double jack and coke guy was an asshole (amusing but still an ass) and treated me like I wasnt wearing anything(I had steel toe boots on, loose trousers-like loose in the legs not form fitting, and a loose shirt that was buttoned up to my collarbone and the sleeves went to my elbows) but double crown and coke guy was really nice, apologised for his friends behaviour and gave me a $100 bill and told me to keep the change. Unfortunately at that job I was lucky to walk away with $5 in tips for the night (we were expected to tip our bartenders out of our tips) for most nights because my managers hated me and put me in terrible sections. As someone who has worked their ass off going through a crowd with a heavy tray of drinks and food and only gotten $1 tip on a $40-50 meal I know how much it sucks.
If a restaurant is visibly busy and I see the server making the attempt to do their best (y'know not intentionally ignoring their tables or anything) I'll tip well. However if the server is just ignoring their tables and doing the bare minimum I won't. But that's my general rule. Make the attempt get a decent to great tip. Don't make the attempt get anywhere from nothing to bare minimum for tips.
I judge others on how they tip as well. I've met people who boast proudly that they never tip because of how easy it is to be a server (at which I've interjected and put my personal experiences to them and some have actually changed their policy on tipping because some people are just ignorant and don't know better). My best tip I've ever gotten was from two guys who one ordered a double crown and coke and the other a double jack and coke. Double jack and coke guy was an asshole (amusing but still an ass) and treated me like I wasnt wearing anything(I had steel toe boots on, loose trousers-like loose in the legs not form fitting, and a loose shirt that was buttoned up to my collarbone and the sleeves went to my elbows) but double crown and coke guy was really nice, apologised for his friends behaviour and gave me a $100 bill and told me to keep the change. Unfortunately at that job I was lucky to walk away with $5 in tips for the night (we were expected to tip our bartenders out of our tips) for most nights because my managers hated me and put me in terrible sections. As someone who has worked their ass off going through a crowd with a heavy tray of drinks and food and only gotten $1 tip on a $40-50 meal I know how much it sucks.
If a restaurant is visibly busy and I see the server making the attempt to do their best (y'know not intentionally ignoring their tables or anything) I'll tip well. However if the server is just ignoring their tables and doing the bare minimum I won't. But that's my general rule. Make the attempt get a decent to great tip. Don't make the attempt get anywhere from nothing to bare minimum for tips.