There are very different ways how you can contribute and some of them are very easy. We even consider just complaining a good contribution ;-) As it's always good to know where we can improve. If you indicate a constructive proposal of how we could improve it, even better. If you actually create a pull request and a unit test as part of a jira issue, that's even better.
If you have an idea for a code contribution, just follow the steps below.
In order for us to be able to accept your contributions, we need you to sign a contributor agreement. Download, print, sign, scan an individual contributor agreement. Then send the signed scan to tijs.rademakers AT alfresco dot com.
The 2 most important communication channels with the team are the developer forum and our jira issues repository.
Create an issue in our jira issues repository or comment on an existing issue for the work that you plan to commit. Explain what you plan to do and ask for feedback.
You can propose contributions by forking the activiti repository in your personal github space and then creating a pull request.
Check out http://www.jorambarrez.be/blog/2012/09/24/how-to-write-a-unit-test/ It explains how to write a unit test for a contribution. When you supply a unit test, it greatly enhances the chance of your contributions to be accepted.
Before you submit a pull request, always run mvn -Pcheck clean install and ensure it runs fine. It's good if you indicate that you've ran this successfully.