1) Make sure you are listening to music, not sounds. If you don't love music, you are wasting your time and money.
2) A system is only as good as its rooom. Spend as much time as you can optimizing placement of speakers and components. Moving a speaker 3 inches can change the sound more than a new pre-amp!
3) If at all possible, buy it used. This especially applies to cables and cords. It probably does not apply to analog cartridges.
4) Understand the technology and it's strength's and limitations. If you have a tube amp, understand how to properly bias the tubes and when to replace them.
5) Trust your own tastes, realizing, in time, your system should reflect your musical values. A person who mostly listens to String Quartets will most likely end up with a different flavor than someone who is into heavy metal. This is ok., no one has a system capable of reproducing a live perfomrance perfectly, they are all colored to some degree, and that's just fine. You know, some people like chocolate, some like vanilla; neither of these is "right"
