To each his own

I'm sure everyone has their own take on the answer however, for me it was railroad locations and era that I remembered fondly from my youth. There were three such locations none of which were the same railroad. I used the three areas as LDEs and assembled them into a plausible fictional railroad. Now the railroad is not only an opportunity to model prototypes (to a degree) it also reminds me of more carefree times. Each of the LDEs mean more to me than just an accurate miniature world, they are relevant to treasured memories.

Hence the tagline of my railroad - LK&O Railroad, A Railroad with Relevance

I think the ibggest issue is what you like.

In my first layout, I tried to put way too much into the layout and ended up with a "bowl of spaghetti."  I then decided to do a point to point in HO and was going to model the Surf Line with Union Station in Los Angeles at one end and San Diego at the other end.  When I picked up a book on the Los Angeles Union Passenger Terminal and saw how large it was, I realized that I didn't have room to model Union Station, let alone the rest of the Surf Line!  Then I joined a modular club and discovered that I get bored with just running trains in circles no matter how big the circles are, and that included a modular set up at the 2008 NMRA convention in Anaheim where we had a layout 120 feet long by 90 feet wide at one end and 60 feet wide at the other end with an inside corner halfway down one side.

I decided to build a switching layout modeling the entire Vernon, Ca side of the Los Angeles Junction Railway.  After all how difficult should it be to model a railway that measures less than 1 mile wide by perhaps 3 miles long.  After visiting Vernon and doing some extensive exploring, I discovered that I don't even have enough room for that and have now decided to do a freelance version of the LAJ featuring two or three industries that I want to model and a small yard.  After reading Lance Mindheim's book How To Operate a Modern Era Switching Layout, I've realized that less can be a lot more if you try to be halfway prototypical with your switching moves. 

How to decide indeed!

Since taking a chainsaw (figuratively, not litterally) to my previous layout last fall, it has taken me a couple of false starts and a lot of soul searching to come up with the concept and design for my new layout. For a while, it was driving me bonkers!

In the end I wound up using my own version of John Armstrong's famous "Given and Druthers" and it really helped me figure out just what I wanted.

I figured that I liked (relatively) long trains, with big six axle diesels running through rural eastern type scenery. I also prefer mainline running to switching so a big yard (at this time) wasn't that important to me. I wanted a fairly low ratio of track to scenery - single track with passing sidings.

Finally, if possible, I wanted the option of maybe backdating the layout to include heavy electric operations - probably Pennsy or one of its successors, although the Milwaukee Road would be acceptable too.

When everything was tallied up and applied to the space I have available, it was really somewhat amazing! Many years ago, when I first got into model railroading as an adult (roughly the mid 1980s), I thought it would be fun to model the PRR's Port Road (run by Conrail at the time) which runs along the Susquehanna River from Perryville Maryland to Harrisburg's Enola yard. I lived in the area and made countless railfan trips to Port Deposit, Perryville Columbia and points in between. However, at the time, I didn't have room enough for anything larger than a small switching layout.

However, the more I researched the line, measuring it against my aforementioned Givens and Druthers the more my instincts of all those years ago proved to be spot on. The Port Road would be just what I was looking for and now I had the room to do it justice.  Eventually it got to the point that I felt confident enough to start drawing a track plan.

So, long story short (I know, too late!) I took what I liked to do in model railroading and then searched for a prototype that satisfied the majority of those likes.

Look this over

Shellback It sounds like you have an idea but need to narrow the focus to a practical level.  Try downloading these notes to look them over and see if it doesn't guide you  http://layoutvision.com/id51.html.  

Steve

What are your goals?

I guess the real question is what your goals are for the layout?  Do you want to run trains from one place to the other, or do a lot of switching?  Are you more interested in operating the layout, or just sitting back and watching trains run?  Do you want a realistic representation or do you just want to capture the feel of Cowtown and North Texas?  Or perhaps all of the above?  There are a LOT of modeling possibilities in Fort Worth.  If only there were basements here in Texas...

One of the things to think about as well is the availability of equipment for your railroad.  One of the most difficult things for the transition era is the unavailability of suitable steam engines.  If only someone made a T&P 2-10-4 then life would be so much easier (though I believe there may actually be suitable models on the market to represent the MKT steam fleet).

My opinion, and take it for what it's worth, is to pick out a few key elements from the area (the stock yards area perhaps and Tower 55, or some of the smaller yards in the area) and incorporate those into a layout that provides operating potential.  That is, make sure it doesn't become a static display and is something that gives you real "playtime" otherwise you'll lose interest.

By the way, I think modeling the Fort Worth T&P station in N scale would be REALLY cool...