While this may seem to be compulsive, the more you know where every piece of track, street, building, etc. is to go the better design and operation of your layout will be. Things may change but have a comprehensive idea.
Granated if this is your 1st layout, there are bound to be problems. Consider these to be part of the learning curve. Very few individuals build a 1st layout without any problems.
If you are planning on building a layout which appears in a model railroad book on layouts or copy someone else's layout there is still pre-planning to do. Before doing anything consider the following -
As you do your planning, keep in mind the following - do you favor primarily the running of a train (turning the layout on and just running a single car or train around for a while), switching, or a combination of the 2 methods of operation? Do you want an oval layout (There's many forms of ovals which do not look like ovals.) or a point to point layout - an in, reverse, and out style?
Buy some layout planning books (booklets) which have layout plans. Ask your friends if they have some booklets you can borrow or buy used copies of layout planning booklets. Get as many as you can for your planning-the-layout phase. Read them!
Look at track plans with a pencil or a blunt pointer to follow the track as though you are operating a model (train) over the track. Does it make sense to you? Follow all the possible routes. Do you like it? Would it suit your needs? Can you or your friends install trolley wire over it (if you plan on operating trolley models)?
My father purchased a booklet titled "Model Railroading Track and Planning" published by Kalmbach in the late 1940's. I still have the booklet. It has all types of layouts from simple ovals to complex multi yards and tracks.
These are the cover and pages from the booklet regarding a trolley layout. As you read the pages keep in mind the era in which the material is written and what trolley models were available the late 1940 and early 50's.
In the late 1940's there was almost more S gauge trolleys available than any other gauge. This is the reason the track plan was drawn for S gauge. Just a few years later Ken Kidder started to import brass O scale trolley bodies and Rich Wagner started making O scale power/trail trucks and parts.
The trolley layout plan reproduced above is a walk around style of layout. If each side is extended, the layout could become an along the wall layout where you and your friends could walk in the center of the layout.
Also, visit as many operating layouts as possible. Do you like how the layout operates? Do you like the track plan?
Ask the owner how he or she developed their track plan.
Ask about electrically wiring the layout.
Ask how the control panel was designed and built.
Ask about building the layout.
Ask about the installation of the trolley wire.
Ask about how the layout is operated - models just run arround or on a planned schedule of operation.
If there is not enough time to find out about these items, plan a second trip or a way to talk to the owner in the future.
Let's look at each item separately - Ask the owner how he or she developed their track plan. You want to find out the what and why. Something which helped me to understand what can fit into the available space was to make a couple of photocopies of the track plan. The photocopies were cut up to see if the layout would fit into my space.
Ask about electrically wiring the layout. In the past several years space-age electronics and computers have had a interesting inpact on wiring and operating layouts. Individual powered cars can be controlled individually or in sets. Many feet of wire are no longer required. Models can have sound and operating lights controlled from a central location. Are you going to wire up your layout the old way or the new way?
Ask how the control panel was designed and built. This aspect is listed separately because there are multiple methods to controling the trains. There are both centralized and decentralized methods of control and operation. If you read enough about control panels you will find out how to make very professional looking panels. Newer electronic control methods may not require a control panel.
Ask about building the layout. There's a couple of items to check out here. Some guys build their entire layout by themselves while others have several friends with different talents build the layout. What's the pro's and con's of either. The other item to sort out is the priority (flow) of the steps to be done to build the layout. What is to be done 1st, 2nd, 3rd, etc. Also, find out what happens if the flow is jumbled-up.
Ask about the installation of the trolley wire. There are a few ways to install the trolley wire. One thing they have in common is to have tension on the wire as it is installed. The wire has to be soldered to the suspension wires. The line-side poles can be made of metal or wood. The poles can be of different sizes and/or forms such as the CNS&M towers in the Skokie Valley.
Ask about how the layout is operated - Models just run arround or on a planned method of operation. Some layouts operate on a schedule exactly like the prototype. Trains are made-up of a fixed number of cars with trains stopping at stations. the operation of the model trains includes real life problems. While other owners of layouts like to see models running. They turn on the power and the model runs.
Add any topics in which you are interested. Find out as much as you can. Your friends and other's experience in what they do or don't do is important. Nothing beats experience.
I've seen multiple layouts started but not finished because the owner-builder forgot to find out about the steps required to build a layout. A layout is built one step at a time. Each step is a separate process. Sometimes a skipped step is hard to correct.
When building an around the wall layout, I discovered after trying to build 2 other along the wall layouts the 1st step was to paint the walls sky blue, The next step was to install what looked like wallpaper with trees and rolling hills. An industrial scene was install on a separate wall.
For the 3rd step a painter was hired to paint clouds on the walls. Then and only then was lumber cut to build the along the wall layout. As you can see, the beginning steps had nothing to do with cutting lumber.