I just realized that microtasks are not even mentioned in this doc. I don't have time to make a proper edit now, but here goes a rushed description: microtasks are key for candidates and mentors to understand the skills required for a project and whether the candidate has a basic handling of these skills. They are also a good opportunity to start working together, show communication styles, and other practical details that a project application alone will not show. The basic type of microtasks are existing open bugs related with the area of the project idea. Be careful to offer a combination of easy an not so easy bugs, but never tasks that would take more than, say, a full day of an experienced contributor to fix. micro-tasks. :) If there are no open bugs (lucky you!) then first basic tasks related with the implementation of the project idea are good as well.
