Hey OP, recently employed 1L here. From my limited experience, I think it depends on the kind of firm and why they do these events. I've found them at worst to be free food and at best a means to differentiate myself and secure a callback. Grades are incredibly important (and ties to some markets, like mine), but I figured I waste tons of time during my day on Facebook and TLS and goofing off with friends, so I allotted my time accordingly and treated it like any other after school activity but with a suit.
Why I think I was successful: I made sure to greet everybody, but to focus on a particular person or maybe two people (mine were smaller events--smaller market/smaller law school) and really just be genuine about learning more about them even if I didn't have a lot in common or thought them kind of boring. Coincidentally, during one of these things, I hit it off with the hiring partner of Firm X. I thought he was kind of condescending and showy, but I was genuinely interested in getting to know him because I really liked Firm X.
When Firm X held a pre-OCI reception, the hiring partner greeted me and called me "[name of thing we bonded over] girl." Even though I found him condescending, I found myself quickly being introduced by him to other associates at the event AND my classmates who hadn't gone to previous events looked at me like

because the hiring partner "knew" me. The OCI interview was incredibly smooth (probably one of my best) because I felt very comfortable and I was extended a callback the day after.
I don't think it hurts to treat these events as nothing more than a time to learn more about a firm and a practice area. I found it easier to ask more "detailed" questions when I'd talked to partners and associates because there are things you just can't learn from the website.