1) not making People the top priority: cultural change. This requires executive commitment, inclusive consultation, cultural fit, communications, training, marketing, fun etc etc
2) not putting Process second after People: never mind what will it look like or run on; how will it work? Forget the things and look at the actions. Listen in your next workshop: how many people are stuck on nouns and how many are talking in verbs?
3) not leaving Product/Technology/Things to last. Once the process is understood, THEN we can plan the forms, the schema, the cool software... and then we can write the documentation ONCE.
More on this
at the IT Skeptic