I started a lunchtime club at work last year. Twelve people signed up, most of whom had never played, and I had one hour a week in a conference room with a door that did not quite close.
Three things got them to come back.
I did not teach the rules first. I dealt, did one Charleston, and let them play badly for twenty minutes. Questions came naturally and stuck, because they were answers to problems they had just had. A rules lecture beforehand would have lost half of them.
I gave everyone the same hand to aim at. Twelve people trying to find their own line on the card is chaos. One cheap, obvious 25-point hand, played by everyone, meant the first game finished and someone won. That mattered enormously.
I said out loud what I was doing. Every discard, every decision, narrated. "I am throwing the 9-bam because I have nine cracks and no bams." Beginners cannot learn from silence, and the temptation when you know the game is to play quietly and fast.
Nine of the twelve came back the second week. Six are still playing, and two of them now beat me regularly, which I am choosing to describe as a success.