When preparing for a hearing, try to come up with a set of questions for your witnesses/clients that will help establish the facts on which your case is built. You are not allowed to coach a witness/client by having them memorize a script, or by telling them what to say or not say, but you can help them communicate their side of the story in a clear and convincing manner.
Once you have a good starting list of questions, go over them with your witnesses/clients and make revisions from there. If at any point you receive an answer that you think could be detrimental to your case, you can change the wording of the question, or scrap it altogether. You may also want to prepare your witnesses/clients for some potential questions the opposing party may ask during cross-examination.
Once you have finalized your questions, try to go through them a few more times with your witnesses/clients. This can help reduce the chances of them freezing up or forgetting what they want to say on the day of the hearing.