1. No Castle Doctrine as of yet, but it is on the House floor for review. So no shooting bad guys unless you feel threatened, and if you shoot them in the back you're in the wrong.
2. No requirement to inform a LEO of a concealed firearm, but doing so tends to yield good results in most cases. From personal experience, it's very beneficial to do so in most cases. Especially when your cards are in the pocket under your CC.
3. No carry in schools, official buildings (courthouses, city/county office buildings, jails), or casinos. Carry anywhere else you please unless a sign is posted or someone asks you to remove the weapon from a place of business.
4. Any legal resident over the age of 18 can open carry a pistol or long rifle while walking. But the moment they enter any type of enclosed vehicle it is considered concealed and they are in violation of the firearm code. A permit is required in such cases, but oddly enough can't be acquired until the age of 21. The permit fee has been reduced now from $25.00 to $20.00 with the modernization of the processes involved (NICS, on-site photography and permit making)
As most things in PA, the website is a chore to find things out as they change the laws constantly it seems. As long as you stick to those 4 basic rules, you have much of nothing to worry about in PA. Distribution of permits is handled by your local county Sheriffs department (except in Philadelphia since it is a "City of the 1st Class", permits are distributed by the Philadelphia Police Department) while enforcement of firearms laws in PA fall to the State Police, while the Attorney General mostly handles reciprocity.
Overall, we're a pretty 2A friendly state. As long as it's not a full auto weapon in state ranges, and no shooting within your city limits if the local laws frown upon it, you're pretty much good to go. You can apply for a non-resident permit in Maryland, Washington, and Massachusetts to broaden your carry range. No carry in New York, New Jersey, or Ohio. But feel free to run down to West Virginia or Virginia all you want to either purchase, sell or carry weapons. Not sure if there's a waiting period in Virginia, but i know West Virginia was like buying a gun locally here in Pittsburgh.
For more info
Washington County Sheriff Firearms Division
Allegheny County Sheriff Firearms Division
PA State Police Firearms FAQ's
PA Attorney General Firearms Reciprocity