The idea is to first identify the varietal. This can happen at tastings, at a friend's house who's having you over for dinner or by following the advise of your favorite wine shop consultant.

Be innovative, try something NEW every now and then or if you already have a favorite, buy a bottle, take it home and read all about the varietal on the internet or your favorite wine publication.
You will soon discover that the same varietal grows in many parts of the world and some wines are ridiculously overpriced while some represent a great value.

Just keep this in mind:
TASTE + PRICE = VALUE

For example, Cabernets are produced throughout the World and while some prefer a Cabernet from California, others may praize a Cabernet from South Africa, while others may have discovered a great Cabernet from Spain or Chile, maybe Oregon.

The idea is to dicover a wine which is not as popular as the leading best seller and get value, which is the resulting equation between taste and price.