Before getting involved in proceeding before the USPTO make sure to familiarize yourself with the process. As the proceeding begins a number of evidentiary presumptions and rules will be factors. Such presumptions can involve the basis of the application, dates regarding use, and continuous use amongst others. There are other rules that both parties will have to follow. Rules govern nearly every aspect of the process and apply to, but not limited to, amendments to marks, withdrawal of the application or opposition, deposition, discovery, what material is evidence, third-party use, and what evidence is considered admissible. Pleadings must be filed according to such rules. During the discovery phase all prescribed deadlines must be followed. The discovery period, along with disclosures and the trial, will be covered by a standard protective order. Discovery will include a conference, initial disclosures, interrogatories, document requests, and depositions. If a party is failing to comply with an aspect of discovery a motion for sanctions can be filed.
This blog is not legal advice and is not specific to your application. You should always consult an attorney.