I tip according to what I have in my wallet. If I have money set aside for some things, then I try not to unballance my budget. If Im doing well, I dont think about it, I do a quick 15% tip calculator, and then think about how long this person worked.
Never less that $2 for your simple 1 person stop and gos. Mostly thats over 15% since the meal and drink ends up being $8.00
Rarely more than $5
If the service is outstanding, and the food is too... I give what I can. ie: If I spend $70 (nice date not cheap food, but not super expensive.) That server spends $10 minutes on us total. So Its hard to want to spend that much money on a nice night out, but then give that person a $10.50 tip. To me thats way to much to pay someone for smiling to me, asking me a couple of questions, and bringing my food and bill to my table. If everythings perfect, maybe I'll give them the 15%, if the slightest part bothers me.. $5 bucks. Which doesnt make me feel bad since if its not busy, they could have earned the tip, and if it were busy, then they have more tips comming at them.
If someone screws up everything, and im in a bad mood, I walk out. If Im in a normal or good mood, I see if the server is smart enough to make it up to me with some form of complementary something, like some places offer you a side dish or drinks. This server is smart, I then tip him more, if they ignore me I tip them less. I can careless if they earn their living this way, Its not my responsibility to ensure that they succeed, its their own. Thats why they do the simple steps and its easy going. Greet, Introduce, Order Drinks/Appetizers, Serve Drinks, Order main course, Serve Sides Main course, Ask if everything is okay mid-meal, and then ask if they want dessert, serve more or drop off bill. Someone that messes this up slightly is forgivable, but someone that is in LA LA land screwed themselves.
Anything that requires delivery, even if the food is late, I still try to give them atleast $1 more than I would at a dine-in.
I like to eat out, infact I eat out a lot. I think being a customer is just as important as tipping. Theres no reason a server should ask for more. You could have brought service elsewhere = no job opportunity, no tip at all.
You also notice that being a returning customer and familiar face improves your relationship with the server. If you find yourself returning to a place often, make sure you slip a big tip in. That server now remembers you and will treat you much better, and you can get away with not tipping as much from then on out, but you might not want to stiff anyone.
Also tip anyone that deals with your property. Utility people, Movers, and sometimes your waste management(if the same people get your route.) Slip your mailman a 5 spot once in a while, even though thery are hard to catch sometimes. Just make sure they are reoccuring faces. You'll notice the trash that gets tipped over is now cleaned up, the small packages that usually gets jammed into your mail box on those rare occasions are delivered to your door, the paperwork that your cable guy screwed up is no longer screwed up, but hooked up, your movers didnt play basketball with your lighter/fragile boxes...ect ect ect...
Im no cheapskate. Im a little better than *Fair* , or atleast I like to believe that I am.