After a lunch-time discussion about branching strategies with TFS I started looking for a good branching guide.  The ALM Rangers put together a thorough guide based on lessons learned from real-world deployments.  The guide provides general guidance for selecting one of four increasingly complex strategies:

• Basic: Main, development, and release branches
• Standard: Basic + service pack branches
• Advanced: Standard + hot fix branches
• Mature: Single main branch with multiple development, service pack, hot fix, and release branches

Equally important is the discussion about when to create additional development branches:

• Breaking changes: A change in a common library will break other parts of the system until they are updated to reflect the change
• Segregated feature work: A team wants to control when its features are released to other teams
• Next version development: Allows development on the next version to start before the release branch is created
• “Scratch” or Temporary Branches: Prototype work, etc…

If you’re looking for a decent branching strategy guide I recommend starting here.  The document is a pretty quick read and well worth the time spent reviewing it but make sure you take some time to review the supplemental materials as well.  They have a lot of good information that can help clarify or extend the information in the main guide.

Guide: http://tfsbranchingguideiii.codeplex.com/
ALM Rangers: http://msdn.microsoft.com/en-us/vstudio/ee358786.aspx