BYOB Rules in Pennsylvania
The Pennsylvania Liquor Control Board (PLCB) says, "Pennsylvania liquor laws do not prohibit persons from bringing their own beer, wine, or liquor into unlicensed (or even licensed) premises, so long as the alcohol was legally procured under Pennsylvania law and the owner of the premises allows such a practice. There is no special permit or license required from the Board for such activity." It also notes that it is the Pennsylvania State Police, Bureau of Liquor Control Enforcement which enforces the liquor laws in the Commonwealth.
The PLCB offers some other good advice: "Because local ordinances may restrict 'bring your own' alcohol establishments, however, you may want to check with the local municipality in which the restaurant is located to see if any such ordinances exist. Also be aware that licensees may have their own 'house rules' concerning customers bringing their own alcohol into the licensed premises. If a licensed premises does not wish to permit this practice, it may prohibit customers from doing so, as long as it does not do so in an unlawfully discriminatory manner..."
It is up to the owner of the restaurant to determine if you are allowed to bring your own bottle.
The best suggestion is to call ahead to be sure a restaurant will allow you to BYOB, and if they do what is their policy. Some establishments will chill your wine for you, provide you with glasses and even open and pour the bottle for you. Some do this free of charge, other charge a "corkage" fee. At other establishments you must provide your own glasses and corkscrew. There is no standard. Be prepared.
The most important advice is to never drink and drive. Whether you bring your own bottle or purchase one from a licensed restaurant, use a designated driver.