Research, and a healthy dose of it.
I recommend looking through a lot of other users' profiles to find out what hardware is popular in the community. If you have something that everyone else has, chances are better that it's going to get software support, and that it's going to work without much hacking.
If you have a significant other that will be depending on the system, setup the system on the side first (in "non-production" mode) until you learn the ins/outs. Learn from my (and many others') mistake!
Though the system and documentation is intended to be usable by the nearly-computer-illiterate, it's definitely not achieved that yet. If people in the forum aren't answering your questions, there's a decent chance your question isn't specific enough, or your answer is easily found in the wiki/forums... This crowd isn't overly tolerant of those who are not resourceful.