I believe that since the law applies to everyone, it should be accessible to everyone. Unfortunately, the law has become so complicated that its practice has become a profession. While you are permitted to represent yourself, it is not always the best option. Employment law can be complicated, and I recommend that you seek an attorney with experience in the field.
I know that you are looking for more guidance than "hire a lawyer," but that is, for the most part, all that I can offer. If you are going to continue without an attorney, the only other advice I can offer regarding how to prepare for a deposition is that you should keep in mind the elements that must be proven to sustain the action at issue. If you are taking the deposition, seek out the facts that will prove your case. If you are the despondent, your obligation is to respond truthfully, and that is all that you can do without learning applicable objections along with when and how to raise them.
Unfortunately, it just is not possible to help you with your issue/question in this forum. Lawyers assist their clients with preparing for a deposition by sitting down with them and going over issues in the case. Your decision to represent yourself means that you are in the position of having to help yourself with your preparation. The only viable response that you can be give here is "hire an attorney". Well, there is additional information... "be honest (f you are being deposed) and thorough (if you are doing the deposing)" and "review the facts of your case prior to the deposition."
I hope this information helps answer your question(s).
~ Kem Eyo
The above answer is a general explanation of legal rights and procedures. It does not constitute legal advice. Nor does it establish an attorney-client relationship between the individual posting the question and the attorney providing the answer.
As the other attorneys have advised, you need an attorney to help you prepare. You can contact legal aid. There are actually a lot of underemployed lawyers out there today who may be willing to represent you solely for the deposition for a reasonable fee. You can call the Atlanta Bar Association and ask for their lawyer referral office.