You’ve got a complex new product you are wanting to bring to market, at what point do you start developing?
There are those who will say that you should start immediately, but this can lead to going down too many dead ends and just waste precious development time.
Others will tell you not to start until you have all the requirements ironed out and a full specification. Whilst this does stop the dead ends mentioned you’ll end up moving so slow that you are constantly behind the competition.
A good rule of thumb is to get around 70% of the requirements ironed out before you start developing. The first 70% of requirements tend to be the easier to get, with the remaining 30% being the edge cases we all know and love.
By starting at 70% you’ll know what what it is that you are heading for, and have the broad outline of how you are going to get there. This won’t entirely eliminate some wrong choices being made in development, but the few items that you need to re-do will be more than made up for by the speed that you can bring your product to market.