Here's what I do:
When I play a multi-player game, I click on the player to show their profile. It the player isn't a club member and I think he/she would be a good addition to the club, I'll just ask if they'd be interested in joining a club.
About 10% of the time I get a yes, and thus a new member.
To delete inactive members, just click on the member you want to delete and select delete.