I only tip if it requires that I go through a waitress or bartender, those people are only paid if they are tipped and I don't expect them to serve me for nothing. If it is a hostess (who is on salary) I generally do not tip.
No way. If it's a waiter or bartender, all the work required is in merely taking the order, ringing it up, and maybe taking a few minutes to check on it and make sure everything is ready and bagged/boxed properly (e.g. drop napkins or plasticware in with the food). You're really not taking much of their time or distracting them from performing their duties for customers who are dining in. In the cases of hostesses, counter personnel, or specific to-go servers, all of them make a higher hourly wage, which means there's no expectation of tips built into their pay structure. Anyone who tells you otherwise is most likely a service industry person who stands to financially gain from people tipping where they don't need to do so. I speak as someone currently working a bartender, so there is some experience behind my opinion.
Never unless I made picky special requests that took a few minutes to take care of. In other words, never.
Related question that probably requires its own poll: do you tip in a place where you order at the counter and bus all your own food, in other words, no waitstaff? It's a dilemma. Typically I will either dump my change in their tip jar or if I leave my dishes/mess at the table I will tip a couple dollars for the hassle. I feel bad for the people who work in those places though, as a lot of people leave their stuff behind and don't bus it and don't tip, which I think is probably out of line with expectations.
I might if I was a regular at some place where tipping might be appropriate, but I'm not a regular at any such place, so the answer is, no, never. For example, sometimes I order takeout from the diner. When I go to pick it up, if I sit down at the bar and have a coffee while waiting, then I'll leave a normal tip, but if I just walk in and the food is ready to go and I get it from the host/hostess, then I don't leave a tip.
When I lived in Atlanta, I used to grab takeout for about 5 or 6 friends form a certain place every couple of weeks. The bartender there would take my order and usually offer me a free beer while I sat at her bar and waited. This warrented a few bucks from me...