You saw Mookie's response to your other question, I assume? Here in northeastern Illinois, TimChgo and I are among those who are blessed with not having to go out and chase 'em down.
So I can only echo Jamie when it comes to safety on the drive. Get yourself far enough ahead of the target to give yourself time to do things right.
If you're chasing just any train, be aware of the railroad you're "working" as much as possible--mileposts, signals, detector locations, and so on. A scanner will then be of considerable help (be aware of laws regarding scanners in the state you're in--they may not be legal). Arm yourself with good maps, and study them well before you go. And make notes and mark them when you find a good spot.
Once you reach your spot, stay well away from the track--you don't want to be accused of trespassing, and you don't want to be hit by anything hanging loosely from the train.
It won't hurt to wave at the crew. Cherish the returned waves or horn blasts--they aren't always forthcoming.
Finally, carry some incriminating evidence with you--for example, a railroad atlas, a copy of Trains, something that will tell someone who wonders about you that this is fairly normal behavior for you.
Remember, this isn't baseball--don't plant yourself directly in front of the train to catch it!
Behind keeping your party safe, the most important rule is to have fun!
Carl
Railroader Emeritus (practiced railroading for 46 years--and in 2010 I finally got it right!)
CAACSCOCOM--I don't want to behave improperly, so I just won't behave at all. (SM)
