A contribution day is for people who know what Drupal is and have worked with it in some capacity. We need people in many different roles to participate and contribute in different ways, not just via code. The most important thing to remember, for both mentors and participants, is to have an enjoyable experience.
Checklist for organizing a small contribution event
Have signage so people know they are in the right location.
Be really nice to new folks.
Welcome each person who comes, introduce yourself, introduce everyone else. Say IRL (in real life) names and usernames. Write down names where people can all see them. Point them to the attendee checklist page.
Here is a checklist/timeline/agenda for participants at a contribution event. Some items are more applicable to large events than smaller events, and some items only apply to in-person events:
New contributors are knowledgeable about their areas of interest but they might not be familiar with the Drupal core contribution tools and process. And, some will be new to Drupal as well. New contributors might be site builders, developers, writers, designers, and so on.
To have a successful contribution event that involves new contributors, you or other volunteers will need to: