Firstly, if you haven't already, be sure to join our IRC channel at #golems on freenode.
We use the Github issue tracker extensively so if there's an open issue you want to tackle and there isn't a person assigned to it, feel free to take it as your own! Make sure to comment on the issue with a remark saying something along the lines of "I want to work on this!" and go forth with it and submit a pull requeset. Once 2 of the main contributors give you a LGTM (Looks Good To Me) or a 👍, we will merge it!
There will be a more comprehensive contributing guide once the project matures but for now, I think this will do fine.