The truth is one can't, and one shouldn't. Today's line-up consists of blends $20 and under, not exactly the hotbed of terroir driven wines, which can be an issue with blends to begin with, so what I'm looking for here is enjoyability. What else can one expect from an inexpensive blend? A whole greater than the sum of its parts.
Blended wines are in some ways a relic of the past, when farmers grew a variety of grapes to be sure to have a crop regardless of the vagaries of the vintage. In recent years, they have become a bit of a last ditch catch-all for many wines, which in and of itself isn't a bad thing. Some great juice, Syrah and Barbera for example, has certainly gone to plump up some less than perfectly ripe Cabernet, resulting in a perfectly decent glass of wine at an affordable price. However, don't expect fireworks and varietal perfection. Sometimes one just has to be satisfied with what one has, because you can't always get what you need.
Red Wine image via Shutterstock