A good way to help is to test, and report bugs. Testing is invaluable in making a piece of software solid and usable.
Patches are preferably to be sent via a github pull request.
Patches should be self contained. A good rule of thumb is to have one patch per separate issue, feature, or logical change. Also, no other changes, such as random whitespace changes or reindentation. Following the code style of the particular chunk of code you're modifying is encourgaged. Proper squashing should be done (eg, if you're making a buggy patch, then a later patch to fix the bug, both patches should be merged).
Commit messages should be sensible. That means a subject line that describes the patch, with an optional longer body that gives details, documentation, etc.
Comments are encouraged.
When submitting a pull request on github, make sure your branch is rebased. No merge commits nor stray commits from other people in your submitted branch, please. You may be asked to rebase if there are conflicts (even trivially resolvable ones).
PGP signing commits is strongly encouraged. That should explain why the previous paragraph is here.
Tests would be nice to have if you're adding functionality.