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Dorm Spam - Dorms and living groups at MIT have unofficial mailing lists where people send out email (dorm spam) announcing events and publicizing their student groups. See Dormspam for details. Students are used to getting a lot of dorm spam and ignoring most (or all) of it. Consider asking students to send dorm spam to their own dorms; people are more likely to look at the email longer if they recognize the name of the sender.
Other dance groups - We've sometimes gotten other MIT dance groups (e.g. Lindy Hop, Waltz at MIT) to share information about our upcoming squares and rounds classes with their membership via email.
Facebook Ads - We tried this in 2013. It's unclear how effective they are, but they are cheap and can be used to target MIT students. Create an event for the intro night/ start of class, then ask Tech Squares members to say they are going to the event, then buy facebook ads to advertise the event. This will cause the advertising to be shown more to fb friends of Tech Squares members, in addition to MIT students more generally.
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