Develop and test your patches locally and then push your changes up to your 'forked' repo on SourceForge, and from there send us a merge request.
Things your commits must have/do:
follow PEP-8 (http://www.python.org/dev/peps/pep-0008/) coding guidelines
contain appropriate tests to be added to the automated testing machinery
pass existing tests (and/or fix existing tests that need to change)
be divided into an appropriate number of commits, one per reasonable "chunk" of functionality
Things your patch will have before it can be merged into branch 'dev' or 'master':
Discussion either on the mailing list or in the merge request, where you submitted it
Code-review (possibly many times as you re-work your patches in response to discussion)
Very small patches might not need much discussion.