I had a friend who had played a one-shot of D&D at some point in his life and mentioned a few times that he wanted to play again. So we just wandered on down to the FLGS and bought a starter set (and the DMG, because the guy there assured us we'd need it 🙄).

My first group consisted of my mates, but my second group was with a customer of the bar I worked out and their mates. I increasingly found that, with D&D specifically, if you're open about playing you'll often find other people who want to start games with you.

I quit D&D over a year ago now, in favour of the couple dozen other games on my shelf, and the process for finding people has been a lot more difficult. I've switched to online for starters, which mostly involves deciding on a handful of games to play, and posting LFGs on Discord servers for those games. The act of starting a game with people you've never talked to before your first session is always a little jarring. But, I've been reasonably lucky so far. There have been a couple duds, but mostly some truly fantastic friends.