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Copy them from previous years (listed in the wiki as child pages) and change the date and location, or get creative and design your own! Be sure to save them into the wiki (pdf and source format) for reuse in later years.
Double check that you have the dates for the start of class and the locations correct. In recent years (as of 2015), we've put QR codes on our posters and made these unique each semester to try to track effectiveness. It's unclear whether this is worth it.
Making copies
If possible, use colored paper, as it stands out more. Try to pick unusual colors, and if necessary go up another price bracket to get colors that fewer groups use. Using color printing can be effective too, but limit its use as it is expensive.
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