I would like to share Five Pillars of Wikipedia Day with you (entirely idiosyncratic and my own)-
1. Wikipedia Day should be documented.
#WikipediaDay is the recommended hashtag to use on social media. Remember to take photos, especially a group photo (with cake!), but also respect the wishes of those who do not wish to be photographed. Consider putting highlights of activities on social media throughout the event, and also think about writing something blog-like more as a summary of the event on-wiki, including if you have a grant report.
2. Wikipedia Day should be an opportunity.
This is probably the largest event of your year for several usergroups, maybe not counting an editathon that is purely editing-focused. Use it as an opportunity to help grow your local community, encourage people to take up different roles in the usergroup, and plan out some of your activities for the year of 2019 (including editathons, regular meetups that are monthly or bimonthly, special events, and grant applications). Have a sign-up sheet for attendees, and consider developing and encouraging people t subscribe to locals mailing lists or social media channels as appropriate.
3. Wikipedia Day should be interactive.
Every Wikipedian is a gift to your event. Encourage everyone you can to give a presentation of some sort. And please actively invite and encourage them to do so, particularly those with underrepresented expertise. The easiest way to do this with little planning is "lightning talks" - a series of 3-minute or 5-minute talks that are mercilessly timed but that allow everyone to share a little bit of their knowledge with the wider community.
4. Wikipedia Day should be fun and friendly.
You should foster a friendly and welcoming space for everyone. Try to greet "new" people and make them feel part of the community. Consider nametags if that helps people interact. Be mindful of the possibility of inappropriate behavior or harassment, and know who are the organizers within your group who will be responsible for enforcing friendly space / safe space guidelines.
5. Wikipedia Day should have CAKE.
This reinforces all of the other pillars, and makes them more delicious.
Thanks,
Richard
(User:Pharos)