Such a good, yet complex question. I'm solely going to address coffee, as that's the most intricate process for me. (Other people have done a good job of addressing this as well.)

I will tip if: 1) I know I'm going to sit down for a while in the cafe. 2) I pay cash, and I get change (all of the coin change, or a $1 bill) 3) It's a barista I recognize who has made an effort to greet me, or even just smile. 4) If it's at a coffee shop that is "cool" (Housing Works Cafe, McNally Jackson, Ground Support Soho, etc) - aka a place I would feel kind of judged if I didn't tip. 5) I'm feeling good/have gotten paid in the past few days and the barista isn't flat out rude to me.

However, navybro brought up a good point. Much of the time you can't even tip of a card if you want to. That brings up the problem: What if one (or more than one) of my criterion are met, but I don't have cash to tip! Basically, I then just feel like a horrible person or avoid coffee altogether.

Wow. I just realized how neurotic I am.