"L shaped of 12x 4x 30" wide" So an L shape with one side 12" x 30" and the other side 4' x 30"
That is a nice size for N scale. Lots of possibilities.
Do you want point to point or a continious loop? If you go with the loop, you can use a 14" R curve in 30" (using flex track any R is possible).
Sounds like you'd like a small yard with turn table - possible even on the short side, especially if the loop is above or below the yard level.
Elevation - are you wanting this all on one level or are you prepared put in grades? On a 12 foot run you can nicely handle two levels.
So many possibilities. I would suggest for sure that you read the Layout Design Primer at
http://ldsig.org/wiki/index.php/Category
rimer
It is a great starting point. The more you understand from that document the better.
Also just browsing old train magazines for ideas. Sometimes it is a good idea to pick a theme or key industry. A logging operation from the turn the the century in the mountains would be a great layout, designed totally different from a urban harbour setting. Pick what you want to model first. Seen some recent layouts based on modelling the track at a steel mill. Can be very impressive. I like the harbour idea so have incorporated that into my layout, including a train car ferry dock. Urban or rural? Time to doodle and think and doodle and think some more.
I spent a year or three in that phase - developed lots of layout designs.
Learned how to use Atlas's free RightTrack (go to the Atlas website to download). I'm told Xtrack is now free and better, never looked at that but I'm sure others here have. Learn to use one of these Rail-CAD programs and design away.
There are annual Layout Planning guides put out by MRR as well as publications just on designing layouts.
Couple more links for you to follow
http://andrews-trains.fotopic.net/c374578.html
http://layoutparty.disisus.com/index.php
and don't miss
http://www.visi.com/~spookshow/layouts.html just for the fun of learning from someone elses efforts.
Have fun and keep asking questions. :thumb:
