When I was a grad student the only time my PI was listed first on a paper was when he actually did most of the work and I just helped with maths. Otherwise the

When I was a grad student the only time my PI was listed first on a paper was when he actually did most of the work and I just helped with maths. Otherwise the PI was last and the grad students and post docs doing the research up front. People doing data collection or other ancillary work were mentioned in the acknowledgement section at the end. When the author count is much higher, like in the thousands in high energy physics, there are different norms like listing the authors alphabetically if the paper summarizes many significant achievements. In the in-between author order is negotiated.