What should I be including in a defendant's initial disclosures in credit card lawsuit?

Include any witnesses or evidence you intend to use at trial. At the very least, you are likely to testify on your own behalf. Disclose yourself. And if you are intending on using your cancelled checks to show payment, disclose those. But with evidence, you must also give them a copy. As a catch-all, I would also suggest that you state that you will also use any witnesses or evidence disclosed by any other party, whether or not later delisted.

The rules regarding disclosures in Utah were recently changed. If your lawsuit was commenced prior to November 1, 2011, the old rules apply, and if your lawsuit was commenced on or after November 1, 2011, then the new rules apply. I will send you a link to both rules so that you can review the requirements. You should review Rule 26(a)(1) for the disclosure requirements. Not knowing what defenses you might have to the claims, I am not able to recommend or suggest specific things that you would include in your disclosures. However, generally it will include documents and the identity of witnesses that you may use to tell your side of the story.