You should gather and organize all the information you can about the debt, as well as the collection efforts of any past or current collectors who contacted you. The past correspondence provides important information about the kinds of charges and interest that have been added to the debt.
If you have copies of your credit reports, you will need those also. The credit reports contain the history of the debt, including the time it was incurred, when it was defaulted, and who may have collected it previously.
If you have any notes about the debt or any taped conversations, threatening letters, or any communication whatsoever with the collector, these can be extremely valuable in reconstructing the collection efforts and any abuse. Whenever you are contacted by a collector, you should note the date, time, person you are speaking to and the content of the call including any abusive language or threats. If at all possible, you should keep these notes together in one central spot. Keep a piece of paper near your telephone so you can keep a log of when the debt collector contacts you.
If you have any witnesses who can corroborate that you were abused, you should get a brief statement from that witness in their own words. These statements will help to refresh the witnesses' memories when you get to trial and provide information to your attorney.