Ensure the bug is actually an issue with asdf and not a plugin. If the bug only occurs when using one tool installed by asdf and not others it's likely an issue with the asdf plugin. Find the plugin repository on asdf-vm/asdf-plugins and follow the plugin creators instructions for reporting the bug.
Ensure the bug was not already reported by searching on GitHub under Issues.
If you are unable to find an open issue addressing the problem please open a new one. Please be as specific as possible when reporting the issue. Include the observed behavior as well as what you thought should have happened. Please also provide environmental details like asdf version, shell, OS, etc...
Open a new GitHub pull request with the patch. Refer to the Development section of the README for the details on how to run the unit tests. Please make sure that unit tests pass on Travis CI.
Please read the creating plugins guide.
Documentation can always be improved! Right now there is just the README and the creating plugins guide. The wiki exists but is in a state of disrepair. If you see something that can be improved please submit a pull request or edit the wiki.
Thanks for contributing!