I've been involved in many QlikView projects over the last few years and on some of these I have been called in to bring them back on track after they have run into problems. Every time this has happened it has been due to the proper consideration not being given to design and best practice at the start of the project. Without a good start things can often veer off course.
I have written a blog posting on how you can avoid many of the pitfalls associated with starting out on a new QlikView project: