Personally I give each character a face, either from a person I know who matches their personality or a celebrity that fits the description, even though sometimes it can be really annoying if the author gives more details on the persons appearance and my character doesn’t fit that lol. I’m very curious as to what other people do.
I also do celebrities. Or more accurately, actors. I guess its just easy for my mind to go with characters I’ve seen act things out. I’m visualizing a movie in my head, so I grab people from movies.