It didn't take many years of working for [a large manufacturing concern who
finished between one and 32 of any given product in a year], and sitting on
groups to determine software solutions, wherein the group was almost always
mandated to look at COTS* packages first, before I concluded:

Hire expert IT staff.  Involve them deeply in the business.  Focus on
business processes. Write your own systems.  Retain your employees and their
knowledge of the business. Educate your users to communicate with the IT
staff.  Educate your IT staff to communicate with the users.  Use formal
methods.  Put out the extra effort to keep your software maintainable at all
times (housekeeping.)  Plan your IT strategies years in advance, and keep
refining those plans.

At this company, we never found a COTS* package that would allow us to meet
our customers requirements and still stay in business (desktop tools
excepted.)  This company is now in about year three (I believe) of planning
their move to SAP.

-dtd

*COTS = commercial off-the shelf