At United we usually meet in the Flight Planning Area (a large room with computers and tables) to go over the route, the weather at the departure airport, destination airport, any alternate airports and the en route weather. We also go over the maintenance history of the airplane. From there we generally walk to the airplane together. We try to be onboard between 60 and 45 minutes prior to departure.
Once we are on the airplane, the Captain usually briefs the Flight Attendants while the FO does the exterior inspection of the airplane. From there we both check the airplane’s various systems and program the Flight Management Computer.
Yes, if you are on the 757 at United you can expect trips to anywhere the airplane flies, both domestic and international. When I was on that airplane it was not uncommon for half my month to be spent stateside while the other half was overseas.