Fast feedback is a cornerstone of agile software development. When developing the LHOTSE project at Otto, we tried to be as agile as possible and many of our means and methods revolve around fast feedback. Here is a list of my favourite things we do to foster fast feedback. It does not at all cover everything we do in our daily work, let alone everything one possibly could do.
All methods have one thing in common: They try to let the development team know as early as possible when things are going into the wrong direction. The key hypothesis is: The sooner you recognize a mistake, the easier it is to fix it. If you introduce a bug in the software, it is easiest to fix it right away, when you still know what you where doing and when you can associate the bug with the small change you just did. When you learn about a bug later, you first have to identify the change that introduced it, then try to remember the intentions of that change. When adjusting the change, you have to be careful not to break anything that was built on top of it later.