A most basic question. The important thing to remember is that everyone, from first time concert-goer to long-time aficionado, has been confronted with this same decision at some point. A certain piece, performer or composer may have caught their attention through either hearing a piece at a concert, on a movie soundtrack, or even a commercial on TV. Once the listener has a toehold then there are a number of different methodologies by which one can go about exploring classical music, and each person is bound to take an individual path.
The purpose of this guide, therefore, is to provide some basic information, including tips on possible avenues of investigation, that will be useful to the novice and experienced listener alike. There is far more information here than can be absorbed in one (or even several) sitting, so be prepared to return here often as your understanding of, and familiarity with, the music that you find interesting expands.
Some ideas on methodologies for exploring and learning about music.