- Use virtualenv to keep your application's dependencies together.
- Use virtualenvwrapper to keep your virtual environments together.
- Keep track of dependencies with one or more text files.
- Use a version control system. I recommend Git.
- Use .gitignore to keep clutter and secrets out of version control.
- Debug mode can give you information about problems in development.
- The Flask-DebugToolbar extension will give you even more of that information.