Whenever you have unique knowledge and experience a jury likely doesn’t, and you can communicate your opinions effectively, you are much of the way there.  Your credibility and credentials will be scrutinized by attorneys and the Court, so you have to pass muster.  A good place to start a career as an expert witness is to be a “consultant” to the attorney and not a “disclosed expert witness.”  As a consultant, you are simply sharing with the attorney your insights about the case, including about counterpart experts on the opposing side  You’ll learn the limitations of your knowledge, and attorneys will tell you if your perspective is helpful.  They may end up retaining you as an expert witness.  The transition from consultant to Expert has been an established border in case law subject to different protections and duties.