How sprint "0" it is defined by many people?
- Groom your product backlog to make it usable to plan and estimate
- Create a minimal environment that enables the writing of quality code
- Clean up technical debt carried from the previous releases
- (middle-management trick) Buy-in some time before team is really ready to work on the next release
RULE OF THUMB: Sprint "0" signifies "0" value, hence, you don't really need it to deliver value as per Agile concepts. Sprint "0" may be a necessary investment to get your team ready to deliver value. However, sprint "0" should not be a norm rather it should be an exception. As an example, driving lessons (sprint "0") are necessary investment to be a driver but you don't need to take lessons every time you buy a new car.
I am very sure that you were tempted to use sprint "0" (or something similar) at some point of time. Will you make it a norm or just use this an exception to get to a healthy trend? Also, don't forget to check more Rules of Thumb here.
Mr. Agile is explaining Sprint "0" to Amy in the latest discussion in his office.