I spent the morning up at Columbia, in part to participate in the reading group set up by Josh Peek (Columbia) to work through the astroML book. We covered probability distributions and how to compute and sample from them, along with some frequentist correlation tests (which are not all that useful, in my opinion).
The other reason to be up at Columbia was to discuss the streams projects with Price-Whelan. I encouraged him strongly to write the abstract of our paper; I think the earlier you draft an abstract the better; it scopes the project and makes sure everything important gets said. The abstract is the most important part of the paper, so it makes sense to spend a lot of time working on it. We agreed to follow the (annoying but useful) Astronomy & Astrophysics template of Context, Aims, Method, Results. This guidance is great (and, in the end, you don't have to include the headings explicitly, at least if you aren't publishing in A&A).