emcee is developed and maintained in my spare time and, while I try to be responsive, I don't always get to every issue immediately. If it has been more than a week or two, feel free to ping me to try to get my attention. Do not email me directly; all discussion should happen on the mailing list.
Ensure the bug was not already reported by searching on GitHub under Issues. If you're unable to find an open issue addressing the problem, open a new one. Be sure to include a title and clear description, as much relevant information as possible, and the simplest possible code sample demonstrating the expected behavior that is not occurring.
Open a new GitHub pull request with the patch. Ensure the PR description clearly describes the problem and solution. Include the relevant issue number if applicable.
First, read the VISION notes and make sure that your feature is consistent with those. In particular, modifications of the core algorithm or additions of new algorithms are unlikely to be approved. If your feature seems to be consistent, suggest it on the emcee-users mailing list for some discussion before opening a pull request.
Do not open an issue. Ask any questions on the emcee-users mailing list.
Thanks!