Your contested divorce case is going to trial and now you need evidence to prove your case. This is a very large topic and I can only touch on a few of the basic concepts of what proof is acceptable to the court.
Trial issues often include any or all of the following: child support, spousal support, custody, division of marital assets and debts (equitable distribution) and attorney's fees.
Proof at a trial comes from either or both of two sources: testimony (witnesses who come to court and testify) and documents that are admitted into evidence by the court.
Testimony must come from a person who states what they have seen, heard or know. There are many types of objections that can be made by an opposing attorney to limit or prevent certain testimony from reaching the ears of the judge. Therefore, what you or your witness want to tell the judge must fall into the acceptable category and not the excluded category. For example, testimony must be relevant to the issue to be proven, it must be material (meaning the truth of it is more likely to prove the issue than not to) and must be competent (meaning that the source of the information is reliable). Anyone who watches law shows on TV has heard the objection "hearsay". Learning what is hearsay and what is an exception to the hearsay rule occupies a few weeks of law school education. Generally, hearsay is an out of court statement made by someone repeated in court by a person who was not the speaker of the statement. The reason for the exclusion is that the maker of the statement is not in court and cannot be cross-examined to allow probing of the statement and the witness. There are many, many exceptions to this rule but if the statement does not fall within any of the exceptions the court will not allow the statement to be made in court or it will be disregarded.
Documents that are offered into evidence must also be relevant, material and competent. Additionally, documents may have to be originals, may need to be authenticated (meaning that there is proof that they were made by the witness or received by the witness). Before a document is admitted into evidence, opposing counsel can ask questions of the witness to determine the above and then to make objections (if any). A bank statement, tax return or letter mailed or received will usually be admitted into evidence with a proper "foundation". A bill for services might be accepted or might be rejected if the bill does not have sufficient detail to prove that it is accurate and relevant. A bill without proof of payment might be excluded as might a bill that does not have the name of the person for the item purchased or service rendered or is undated or lacking other detail. Newspaper articles usually do not go into evidence as they are often stating opinion or relying upon other facts that the writer is reporting but does not personally know.
Having an experienced divorce trial attorney is critical to be able to not only provide proper proof to the court but also to organize the testimony and documents in a manner that the court can easily follow. Scattered testimony and documents may lead to a less desirable outcome because of confusion. Clients who think that they can try their own case are almost always making a big mistake. There is a reason why law school is three years, there is a bar exam and then there is the actual learning from trying cases and watching other attorneys try cases.