I enjoyed the hobby back when I was in my teens. Forty years later, I am picking it up again.
A few pointers: design, design, design. Read, read, read. Learn, learn, learn. Make a who host of layouts using SCARM. Be prepared to build an initial layout. A second (better) layout and a third (dream) layout. Going through this process will get your skills up to speed.
Get to know some other hobbyists and ask to attend a session. This will give you great insights into whether you want to RUN a railroad or just enjoy BUILDING one.
Buy less, use the best. There is a lot of second-rate stuff out there. It will only plague you with problems - shorts, derailments etc. etc. Buy quality vs quantity.
Couplers: go with Kadee. There are others, but Kadee are the de-facto standard.
Ideal rolling stock trucks: all my research seems to point to using Kadee trucks but with Intermountain wheel-sets (Wheels and axle).
Track: want to build a really sweet layout? Use Fast Tracks hand-built switches for your layout: http://www.handlaidtrack.com/
Switch machines: I like to go manual for most. A lot of guys use Tortoise Switch Machines. Everyone raves about them but I think that they are huge and would love to know of better, smaller, cheaper ones - with all the same features.
Models: All sorts of kits exist out there but EVERYONE (OK a lot of guys) use Tichy for parts like windows. (I love their rolling stock and have built over 50 iron ore and other cars from them.) Exquisite detail and great customer service.
Essentials: get an NMRA standards gauge. Buy a temperature controlled soldering station. Buy a Dremel with a cut-off wheel (for cutting rail). Wayyyy better than snips. Also, buy a serving tray with high sides. When working on the hobby, ALWAYS keep all your tools in the serving tray. Makes finding them much, much easier. Buy a good air brush like Iwata.
DCC vs DC. I am migrating to DCC. Phone Tony's Trains in Vermont for DCC advice. They are fairly unbiased experts and can help you choose the best system for you.
Weight: get your rolling stock to the proper weight: 1 oz + 1/2 oz for every inch of car length. This will help your trains track better.
Open source: The whole DCC open source thing is a bit klugey at present (in my opinion). This could be an area where you may be able to contribute significantly. Meantime, you may want to buy off-the-shelf to get started and then poke around with Arduino and the like for controls (unless you are a total geek).
Lastly, go look at real trains. See them in yards. See them at crossings. Watch them beside you on the highway. Look at tracks and switchwork... Figure out what era and purpose your railroad will have: Switching? Mainline? Steam? Diesel? Commuter? Short Line? Industrial? Mining? Learn all the background about it that you can and use it to dive in and enjoy!!