What do you do if you run into a person whom you've met before but have completely forgotten their name?

I have heard about “face blindness” but I’m talking more of a memory issue. Is it rude to ask what their name is again? What if you don’t want to be rude or appear foolish by asking their name, then what do you do?

I’m usually very good about remembering peoples’ names and faces, but sometimes for the life of me, there will be times I just cannot remember someone’s name. Like last week, I was talking to my mom on the phone and she mentioned someone from my childhood who I apparently used to hang out with all the time, but the name didn’t ring a bell. There are plenty of other people who I remember, for some reason, that name slipped my mind.

Is there a trick you use to remember peoples’ names?