As with wine, it's best to learn how to read the label before you start shopping for olive oil. Olive-oil basics can be broken down into the following rules (with explanations to follow):
The best, most flavorful olive oil comes from the first pressing (also called cold-pressed). With olive oil, there is no second pressing, so if it's not first-pressed, it's been refined and processed using other oils, additives or heat. The two most desirable types are extra virgin, which has extremely low acidity, and virgin, which has a slightly higher acidity. Both extra virgin and virgin are first-pressed olive oils. Pure olive oil is a blend of virgin and refined oils, while olive pomace oil, which is sometimes used by restaurateurs because of its high smoke point, is made from oil extracted from the solids left over from the pressed olive paste. Light olive oil has been processed for a milder taste, but don't be misled by the name -- it has the same amount of calories.
According to the North American Olive Oil Association, 99 percent of all olive oil sold in the U.S. is imported. American consumers can choose between olive oil imported from Italy, Greece, Spain, Portugal and France, as well as some market newcomers from Australia, South Africa and dozens of other countries. While some people swear by a particular nationality of olive oil, this seems to be a matter for one's individual taste buds to decide. In her excellent 2005 article "An Overview of Some Worldly Oils," New York Times food writer Florence Fabricant offers a comprehensive breakdown of the characteristic flavors you should expect to find in different nationalities of olive oil.
Whether imported or domestic, olive oil (like wine) is a product of harvesting, and as with wine, some vintages are more successful than others. Several review sites mention that certain brands of olive oil may be superlative one year and only so-so the next. That's why reviews can sometimes be misleading; an olive grove's output may vary from season to season, both in quantity and quality.
With any small-harvest, artisanal olive oil, be it from California, Sicily or points beyond, availability can be a major problem. Unless you live in an olive-rich area, such as certain parts of California, or a huge metropolis where just about anything can be located, some olive-oil brands are hard to find, but even the smallest producers can market their products online.
If you're really interested in trying a bunch of different olive oils, there are several mail-order olive-oil clubs. Examples include food critic T.J. Robinson's Fresh Pressed club (currently $87 a quarter for three 250 milliliter bottles shipped once every three months), and Zingerman's Monthly Rare Olive Oil Club (one 500 milliliter bottle per month plus bread for $75/month).