It's time to talk turnouts.
You first need to decide if you want a "switching layout" in which usually short trains serve industries. These types of layouts can provide hours of endless scenarios as train cars are moved from one industry to another and back.
If you opt for a "normal" layout, you still will likely need to add turnouts to your plan as they can be useful in providing more realistic operation.
In real life, two trains often use the same mainline - going the same direction or, well, not. Now, lets assume we all understand why not having a way for a train to pass another would be bad. Let's also assume that we all know why serving industries parked along a mainline could be a bad thing with only one track to use.
It'd be like having the loading dock to a grocery store right on the street. Trucks park to unload and traffic is backed up forever.
In our miniature world, we should keep this in mind.
If you are planning a railroad with a single-track mainline, you should consider "passing sidings."
These are sections of track that include a turnout at either end allowing a train to enter and leave the siding to allow faster trains, or trains traveling in the opposite direction, to pass.
Suppose industries are a part of your railroad. You should consider spurs, either off of the mainline or off of passing tracks. Spurs are tracks that don't reconnect with the mainline. They simply end at or near an industry.
Turnouts come in a number of radii, they come in lefthand, righthand, wye and even 4-way/crossover. They can be curved or straight. They can be operated manually or electronically.
Turnouts with larger radii should be used along the mainline as curves with larger radii make mainline runs look more realistic. Those with smaller radii are good for industrial sidings.
For turnouts that will be situated where you cannot easily reach, go for the electronically operated model. If it is close enough for you to reach, I recommend a manually operated turnout. There's something about moving the switch yourself that makes you feel more connected with the railroad ... kinda like you work there.
My layout is constructed in such a way that all turnouts can be operated manually. I never have to wonder if they are set correctly to make the train go where I want it to go.
For manually operated turnouts, I recommend those without the throw switch attached. I like to add my own throws (made by Caboose Hobbies). They are made for HO and N scales and are reasonably priced and easy to use. They look kind of like the real thing and ensure good alignment of the turnout.
I know, I know, there are a lot of options. There's a lot to think about. Don't just go out and start buying turnouts. This is where a little planning comes in handy.
A little advice ... Don't overcomplicate your layout with too many turnouts, passing sidings and spurs. It'll make your railroad simply look like someone dropped a bowl of spaghetti. A good place to start is to decide how many and what industries might be served by your trains.
Look at some of the track-planning books and magazines out there. That's a great place to start.
For more on model railroad turnouts, visit http://modeltrains.about.com/od/layoutconstruction/tp/turnouts.htm or mrr.trains.com and type "turnouts" in the search window.
Before we go any further with thinking and planning, next week, I'll take a look at some of the tools that no model railroader should be without - unless frustration is something you enjoy.