I've been railfanning as long as I can remember.  In the thousands of hours I've spent beside the tracks, I've been able to make some observations that I feel could help anyone involved in the hobby.  This applies to those just getting started, as well as the old-timers.

First and foremost, one MUST   keep in mind that railroads aren't here for our amusement.  They are here to move freight and people from one place to another.  They are an industrial operation and operate on private   property.  The mere fact that most railroads put up with our activities, or look the other way is remarkable.  Think about it, how many airports allow you to get close enough to photograph their operations?

With that said, respect the fact that you are on private property and close to an industrial operation.  If asked, or told, to leave, do so and be courteous about it.  

Of course, in my humble opinion, the best photos aren't taken at the yards; they're taken in the country. Unless you are very close to the tracks, or climbing on railroad structures, there are very few instances when you'll be asked to leave.

One other thing to think about:  There is no photo, and no railroad activity that is so unique that it is worth jeopardizing SAFETY!  I have seen some very stupid and unsafe acts committed by railfans; that jeopardize the hobby for all of us.  Please, if it's stupid or unsafe, just don't do it, if not for you, for the rest of us!

OK, now for the do's and don'ts.  They aren't presented in any particular order but, to me, they are all important...

DO:  Keep safety in mind ALWAYS

DO:  Respect private property.  Would you like someone trespassing in your backyard?

DO:  Take only photos and leave only footprints, e.g. TREAD LIGHTLY

DON'T: Litter, deface, graphitti, steal, etc.

DO:  Keep a low profile

DON'T:  Display any kind of firearm; leave 'em locked in your vehicle

DON'T:  Drive too close to the tracks; stay on the access roads

DO:  Be courteous to any employees

DON'T:  Hassle railroad cops, foremen, etc. If they ask you to leave, then leave

DON'T:  Act like a moron

DO:  Enjoy yourself!