There are two purposes for the background material and evidence that you will be collecting: documenting the wrongdoing and protecting yourself. You should keep a notebook (and regular backup copies, even of paper material) that both catalogues your evidence and provides the context for it. You should date everything that you obtain, and date the notes you take. Do not do anything illegal to obtain your documentation, but do be creative about the forms of documentation (and how they interlink) than you can get.

Written evidence is some of the most important evidence. Keeping supporting documentation of all kinds is key. You should record all dates and times when events related to your case occur, when you receive or obtain documents, and when you consult with others. If other employees are present when these events occur, record their names so they can back up your story. When recording events, stay as close to the facts as you can, without drawing inferences about motivations that people might have. What did they say? What happened?

If the company tries to fire you or asks you to resign because of specific problems, you will need to have documentation that you are doing your job well and that there are no complaints lodged against you. Obtain a copy of your past performance records. It is possible that there be a definite decrease in scores on your appraisals as soon as you make the wrongdoing a matter of public record. Companies sometime "restructure" in the wake of whistleblowing, and this can be a form of retaliation. Be sure that you have evidence that the company structure is stable before you go public, so you can show the relationship of the restructuring to your whistleblowing and dismissal.