There's no standard for pin direction for manufacturers. But D. Brown posted the norm and S&W's direction. Pins are straight, not tapered generally, so it doesn't matter that much.
However, it's always easier to remove and replace them the same way they were initially installed. And in fact that can usually be observed by studying both ends of the hole with magnification. The clean edged hole is the side that the pin entered. The exit hole is usually slightly bulged around the edge where the pin came thru when installed.
Now that's true for pins that have not been polished over before bluing at the factory like pre mid-1950 S&Ws which had domed pins. After that, all bets are off for observing the pin's travel direction.