Step One:  First Things First
Before any business or venture should ever consider moving away from their current OS to Linux, a clear focus must be defined.

There are three principal categories of Linux use as applied to business environments.  These three categories should be evaluated separately and distinctly rather than all together since any wholesale movement to Linux is bound to fail initially.

All business environments tend to include these three distinct uses for computers: Servers such as email servers; Workstations including graphic intensive PCs or number crunchers; and Desktops for basic PC use including checking emails, writing documents etc.

Any movement to Linux should begin by first defining which systems fall into which categories and doing a bottom line cost assessment for the category itself.  In many cases the most expensive category will be Servers.  However, I've consulted a number of businesses and non-profit organizations where the most significant cost is in Desktops as a result of upgrade costs, licensing fees, and new staffing overhead.

Step Two: Clean Up Terminology
I keep bumping into people who talk about "migrating" to Linux.  In fact, even a few of the editors at reallylinux.com wanted me to use the term in my title so it would convey what most people are thinking.  However, it's a misnomer at best.

Before we overuse or misuse the term "migration" any more, I suggest that in almost all instances, most small businesses want to perform a move to Linux rather than a migration to Linux.