The way to choose the best qui tam or whistleblower lawyer is to find the lawyer that can communicate with you and that has the personal qualities that you feel like you can trust and work with. You need to find someone that has the skill set, experience, and the package of skills to both litigate the case as well as put the case together at the outset that you are comfortable with.
Another important quality is particularly early on in a case. A whistleblower is going to feel a lot of trepidation. They are putting their career on the line, they are afraid of retaliation. Someone that you can talk to you, that you can meet with, and that is accessible to you, that can discuss your case, your fears, your anxieties, and what you are actually going through as a person is a critical quality.