Charles Meyer, a partner in our Montgomery County, Pennsylvania office, wrote a terrific post on High Conflict Custody matters on the Pennsylvania Family Law Blog that he edits. The principles in this post apply to New Jersey cases.
I often tell my clients, that though they may wish to stoop to their spouse's level, that it just isn't worth it and certainly not in the children's best interests. Moreover, if the case is going to be litigated, I want my clients to be "pure as the driven snow" with regard to these issues.
That said, I think that each client going through a custody case should keep a notebook documenting things as they go on. Moreover, save and print provocative emails and text messages and make tape recordings of voice mail messages for future use. As to recordings of conversations, given wiretap and privacy issues, those will be discussed in more detail in a future blog post, and you still must proceed with care.