Documentation
One of the benefits of open source is the ability for the software to be used widely. However, open source software must be well documented for it to useful to anyone outside of the development team. This kind of documentation is different from end-user documentation or manuals, which explain how to interact with the finished product. Good software documentation provides detailed information on a number of areas, including what the software does, how to setup the software, and the license(s) the project falls under. It's helpful to make sure that documentation is written in conjunction with software development to make sure important details are not overlooked (and it's really not fun to do this late in the game). Lastly, documentation should be linked to where the source code is published.
You can learn more about documenting your public repository with:
18F's Open Source Style Guide Documenting APIs An example of a well documented repository