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See Activities Midway.
Recruit vigorously by word of mouth
One thing that I (Alex) did for this (Spring 2012) class was, during the fall and until the class started, when I ran into somebody I knew who seemed possibly interested into Squares, I would encourage them to try it out, and then write down their name. Before the Fun Night and the class I emailed the people I'd written down a couple of times encouraging them to come, mentioning they'd expressed interest before and when. This seemed to work pretty well at getting people to come. (Somewhat key to this, I think, was actually keeping track of people who seemed interested and sending them personalized emails, including ~"I talked to you a couple months ago, and you said you might be interested in Squares. On Tuesday we'll be ...")
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