You can fight a Protection From Abuse case in Pennsylvania by building the strongest possible defense. As the defendant in a PFA, you have to, with the help of your attorney, analyze the complaint, analyze the allegations against you to find weaknesses and holes in the plaintiff's allegations and version of events. Certain matters would be used against a plaintiff. For example, if it took the plaintiff a length of time to seek the PFA from the time that the alleged abuse took place. That could be an aspect that your attorney could use against the plaintiff.
Gathering and obtaining necessary evidence is something your attorney could help you with preparing the necessary witnesses, arranging for the necessary witnesses, then come the time of court attacking the plaintiff's claims and credibility, the plaintiff's witnesses claims and credibility, and by potentially calling the defendant to have the defendant provide a credible version of events or response to the allegations.
There could be an alternative step that an attorney could take also in the sense of fighting a PFA case by arranging an alternative resolution by agreement with the plaintiff and the plaintiff's attorney, which as long as it would be in a defendant's best interest can allow for a different method of resolving the PFA case. An experienced PFA attorney will be able to help you best understand what your best options are and to take the best steps forward. They should be involved from as early as possible in a PFA case.