Generally, what I've found is the reason for the big pile of mess is not that the methodology is wrong, but quite frankly the programmer didn't know what needed

Generally, what I've found is the reason for the big pile of mess is not that the methodology is wrong, but quite frankly the programmer didn't know what needed to be done until the program was completed. Even with a complete set of requirements, if you are writing anything of any complexity then by definition it hasn't been done before. But you can usually take an existing program, re-define the specification, and re-write the code in a much cleaner and correct fashion (assuming you avoid the temptation to add new features at the same time).