Inadequate specification of requirements
Failure to spend time defining and documenting your requirements may mean that you select a system that works perfectly well in certain industries but lacks functionality that is a differentiator in your industry or sector.
The important thing to remember is that most systems on your shortlist will probably do 80% to 90% of what you need as standard. Clearly there’s no value in documenting those requirements – your time and the vendors’ time is much better spent on the differentiator requirements.
Focus on requirements that give you a competitive advantage, drive business benefits, are peculiar to your industry, or that your current systems struggle to manage.