I'm writing a paper with two of my students. Well, I'm writing it with one of them and another one did a lot of work on the statistics. But today we had to straighten out the order that the authors would be listed in on the paper. This can be a contentious issue, and I know of cases in which papers did not getting written at all because the authors couldn't agree on who got to be listed first. Some big multi-author papers simply list everyone in alphabetical order to avoid the fuss, but then Dr. Aardvark always gets to be first author. Some journals have a little section where each author's contribution is described, but they usually end up saying something uninformative and false like "all authors contributed equally."
I came up with most of the ideas in the current paper, put things together, decided who would do what, etc. My student did much of the lab work and is doing much of the actual writing. Given this, most biologists would propose what I did, and what my student objected to: She (as the person doing the writing) should come first, I (as the senior person on the paper) should come last, and everyone else (in this case meaning the statistics student) gets sandwiched in between. This was very counterintuitive for my student; she thought I was trying to minimize my own role by putting myself last. In fact, it is a step up for me to be writing papers in which I am in that last position. I remember this being counterintuitive for me the first time it was explained to me. I was a college student, and a boss said that he'd make me second author on a paper. I said something to the effect that I'd be glad to be even last author, which I thought was being humble, but he took it as me saying the paper had been my idea. We straightened out the miscommunication but I didn't end up being listed as author on the paper. That the last author spot (at least in biology) signifies the senior author is a code biologists internalize, and I had to think back a long way to figure out why my student objected to me being last author. I explained, she reluctantly believed, and now it is settled.