It depends on the theme. If we're picking something in a space the group already knows well, like databases, I'll look at "Best Papers" from recent VLDB/ICDE/SIGMOD conferences. If we're exploring a topic most people are unfamiliar with, we'll go with something more foundational instead. For example, we're starting an arc on datacenters (servers, racks, networking, load balancing, power, cooling, failures, etc.), and most attendees don't have deep background there, so I found a book on the topic that we're going to read through[1].

[1] https://link.springer.com/book/10.1007/978-3-031-01761-2

Not author, but in the past I was just going through papers on biggest conferences for the last year and checked what sounded interesting for my own education. But it was a bit of a chore. What I tried now is use gemini thinking research and asked it to do just that, go through main software/hardware conferences for last 3 years, find me papers on the topics of interest and give summary and links. The result is pretty good!