What does an early-career scientist have to do at conferences besides give a good talk? In my mind, it may even be more important to make a friend. Yeah, sounds stupid but hear me out.
Whenever I go to a science gathering (workshop, conference, etc.) I always make it a mission to get to know at least two people in my field more senior than me, who did not know me personally before. Maybe this sounds ridiculous to decide consciously, but it is really easy to just hang out with the people you already know at meetings. Rather than taking the comfortable route, I ensure that I seek out people so that they can put a face to a name they may have seen in the literature, and numerous good things have resulted from making this effort. I've twice been invited for departmental seminars, started a collaboration, been given useful data as well as feedback on my grant proposals that people had reviewed, all based on conversations that happened or started at a meeting.
Does it sometimes mean that I get stuck in awkward conversations or some painful social interactions? Yup. But I consider it a huge waste if I leave a meeting without having gotten at least a couple of senior people to remember my name and in many little ways this pays off. I'll take an edge I can get right now.