Honestly, you can't really meet anyone at a convention these days. Back in the old days, the 70s and 80s, celebrities would just be walking the convention floor, hanging out at tables, etc. No bodyguards, just people hanging out and you could go hang out with them. That's how I went out to lunch with DeForest Kelley one day as he was hanging out at a convention. And the old-time pro lounges actually were restricted to actual professionals, unlike today, and you'd actually have celebrities going in there to rest. If you had access, as I did, you got to spend a lot of time with them. And so long as you didn't treat them like idols, most were just genuinely nice people that I made friends with. But that's been years. The last time I actually got to hang out with anyone at a con was a good decade or so ago, when John Barrowman was at a booth at a con. We had met a couple of times before and he just invited me behind the table so we could chat between fans. And, of course, I had an annual "date" with Ray Bradbury at a particular place on the floor at SDCC, where we just bumped into each other every single year, totally by accident, and we just stopped and talked for a couple of minutes.
Today, you just can't actually make friends with celebrities at conventions.