To get on, go to where trains stop. Choose a “side out” (where parallel tracks converge), or anywhere trains are known to slow down to a crawl. Obviously, you ought to know where your train is going. Not all trains make frequent stops. Going “west” might mean you go further west than you intended. Knowing where your train is headed might require a phone call to the railroad. There’s no sense getting on a train if you don’t know where it’s going.
Hide, of course, and then make a break for the car you want. If your target car is moving, then you are “catching it on the fly” which is always more dangerous.
It’s better to choose a boxcar than any other. You can usually find one with an open door--and you can see if it’s occupied before you jump in; and boxcars usually have a handle to help you step up into the car. Whatever you do, don’t ride suicide (on open tankers in plain sight). Stay concealed.
When the train begins to slow down, look around. Get a good idea of what you’re dealing with. Railroad cops will probably be waiting around to check the cars. They have to for insurance purposes. Most of the time they have no interest is arresting you, but stay away from them anyway. Hop off as soon as you can safely do so, and run to the second best hiding spot. The best hiding spot might have a cop waiting to harass you. Get off railroad property as fast as you can--that’s the main idea.
