Getting started: Workflow for content development/edits/design

I am an experience Articulate Presenter user, and I am making the shift to Storyline for a new project.  For past courses we had existing PowerPoint files to modify and convert.  This time around the SME is developing the content from scratch.  This gives me more flexibility in the course development, but we are at a loss for how to exchange content and discuss possible interactions and branching.  (In this case, we have only one content author, and he will not be using Storyline. There are a couple of other reviewers.)

• How do your content authors provide their content to you?
• How do you communicate changes to content once it's in Storyline?
• Do you use flow diagrams to document branching logic?
• How do you define interactions?
• Do you use storyboards/mockups?
• What other tips or advice can you suggest for streamlining e-Learning content development?