Hi Popeye,
Welcome to The Gauge!
I would recommend that you look through The Gauge (there is a search tool) to find and read what others have done - there is a lot of information here to help "newbies".
As for planning your layout, I would start with a scale drawing of the space you have available. Draw the walls, windows, doors, cupboards, waterheater - basically anything you have to deal with when you go to install a layout.
You can do you drawing on graph paper, or you can look for some track planning software. RTS from Atlas (
www.atlasrr.com) and XTrkCAD from Sillub (
www.sillub.com) are both free. XTrkCAD is more like a real CAD program - if you choose this one, be sure to do the tutorial to get you going.
Both will help you work out the actual size of the turnouts, roundhouse, etc, so you are not cramming things into the plan.
So what else do you want to do with this layout? Some questions that will help with planning:
- What era/time frame? Steam or diesel?
- Location?
- Railroads you want to include?
- What industries do you want (besides a coal mine)?
- What part of the hobby do you like (so far at least...

)? Do you want to build detailed models? Do you want to run the railroad prototypically?
- Do you want to have friends over to run it with you or do you like to be by yourself?
Take a look for some of the posts by "Triplex" - he has a great list of questions that will help you focus more on what you want to do. That will help anyone who wishes to help you plan.
Andrew