plbab,
Welcome to The Gauge!
Asking other model railroaders how best to start in the hobby is like asking people what is the best flavor of ice cream. You'll get different answers from each of us!
But if I may be so bold... I'd start out small. Pick a scale and go with it. I had many reservations about N-scale when I first started, but decided that I wasn't going to be able to do much in HO with the space that I had available. I'm pleased with my choice, although I have been tempted at times to switch to HO.
N lets you do more in a less space. HO has a greater variety of Ready-To-Run (RTR) locos and rolling stock, and more structure kits. Plus, HO is easier to handle.
But whatever scale you decide on, start out with a small layout. It doesn't have to be a major project--just something where you can learn and experiment. Maybe make something that you can easily disassemble in case you don't like the direction that you started off in. (I say this from experience.)
There are some pre-fab layout boards you can buy. These are modular systems that can be mixed and matched as your layout grows. BUT they are rather expensive.
Another idea is to build modules using the NTrak, HOTrack or other modular standards--or make up your own.
Here are some links that might be useful:
http://www.nmra.org <-- National Model Railroad Association. They have a beginner's guide to model railroading.
http://www.ntrak.org <-- An N-scale modular standard.
http://www.trainsarefun.com/hotrack/hotrack.htm <-- HO-scale modular standard.
http://users.iafrica.com/c/ca/caroper/tutorial/ <-- This web site has an excellent tutorial on building a model railroad. The author starts with a simple plan, then adds on more features. This may be a good way for you to get started. The plans are for N-scale, but they could be easily adapted to HO.
http://www.terrainfortrains.com/ <-- Pre-fab modules in HO- and N-scale.
http://www.trainscapes.com/ <-- Pre-fab modules in HO.
-Rory