Looking for train locations...

[mwhigham]

My pleasure, here is another link. This site is quite particular about the quality of the photos they will accept, so it's a good place to observe some good rail fan technique.
http://www.railpictures.net/

[bburton]

I've yet to do it, but I've been told that the ride on the Trinity Railway Express from Dallas to Fort Worth and back again -- or vice versa -- can be fun.

[mwhigham]

Riding the TRE is a blast. You get to see areas that you probably haven't seen before. If you are a rail fan, you will see yards, sidings and lots of other rail related things not observable from the roads. For shooting photos, the windows are covered with some type of sunshade webbing that will ruin your photographs though.
The DART rail is pretty cool too.
Also the McKinney Avenue Trolley's are fun. I used to drive one and the motorman will stop for you and explain some of the local area for you. Not only that, it stops across from the Dallas Museum of Art and close to the Nasher Sculpture Garden.