Lots of folks have and argue different opions... but thse have worked for me just fine for decades making sure no laws/policies were broken.
Face to face to another resident of your state will depend on whatever that states regs are, whether the firearm is legal in all localities, whether registration is mandatory, etc, and it leaves you responsible for whether the buyer can even own it legally. Any local firearms dealer can tell you your states regs (and advise you on out of state), as can some local officials. In many states a FTF needs no paperwork, but even in those I'd do a dated bill of sale signing the firearm over just to no longer be accountable for it, even if sold to a friend. It's out of your control and so what is done with it, protect yourself.
Anyway, found this easily for a start for PA...
http://en.wikipedia.org/wiki/Gun_laws_in_Pennsylvania Selling out of state you will have to follow all the BATF regs, and those some states/localities have for firearms, especially handguns. Do not ship a sold handgun yourself. Find a local FFL to handle the transfer for you, simple as that and you don't have to know all the regs, federal or state, and the receiving FFL is responsible to find out if the buyer can legally own it. Your FFL will charge a fee for the transfer, but its well worth it for an easy, safe transfer that removes you from any responsibility for it on both ends. It's the FFL's responsibility to make sure no laws are broken, and to deal with any loss or damage in transit. I ask my buyers to include insurance money along with shipping cost, but I pay the TX fees on my end.
Want more, check out the BATF web site where its all spelled out; and for a sale to another state that states regs as well.
My transferring FFL won't ship any regulated firearm to CA, period. But I can ship long guns there myself IF the receiving FFL in CA is a member of that states program AND will accept out of state firearms from a non FFL. Easy for me, no TX fees, all I require is payment and a copy of that FFL license for my records to ship. But I cannot ship handguns to CA myself, so I don't sell any to CA buyers... not unless they want to pay the much higher TX fees another FFL here would charge to do so. Some tack on an additional $75 or more for any firearm going to CA, long or short.
FWIW-HTH
