Ok.. My previous write-ups included installing and configuring workflows and brief description for developing workflows. I got some time to create a document which explains in detail about how to develop workflow artifacts.
I have taken an example of Purchase order invoice approval process.
Here is the document Workflow – Development
Here is the link to the sample XPO of the scenario Purchase order approval project
Note: There are some existing objects that have been modified. The user should take care while importing the project and look for possible conflicts that may arise.