I would try to get a feel for the range of wines available. You might want to approach it from a stylistic angle. I think the classification Mary Ewing-Mulligan and Ed McCarthy present in their book Wine Style has some merits. Some recommendations based on their system:
Fresh, unoaked (light) whites: Soave from Italy or Muscadet from France's Loire Valley. Also, some less expensive Pinot Grigio.
Earthy whites: Côtes du Rhône blanc or other Rhône whites (excluding Condrieu).
Aromatic whites: Gewürztraminer from Alsace or USA, Viognier from USA or Australia (or Condrieu if you have the money), Sauvignon Blanc from New Zealand. You may want two in this category, a Gewürz or a Viognier (both emphasize perfume and spice) plus the New Zealand SB (which emphasizes fruit).
Rich, oaky whites: American Chardonnay.
Mild-mannered reds: inexpensive Bordeaux, or inexpensive Chianti (more expensive wines fall in other categories).
Soft, fruity reds: Beaujolais, Valpolicella (Italy), most inexpensive Pinot Noir or red Burgundy (again, the expensive stuff is more powerful and/or more complex).
Fresh, spicy reds: Chinon (Cabernet Franc from the Loire Valley), most Rhône reds (but some can be mild, check with someone at your store), Barbera or Dolcetto from Italy.
Poerful reds: California Cabernet or Cabernet blends, Barolo or Barbaresco (Italy), Bordeaux (for all of these, if they're inexpensive they are probably not in this category).
Rosé: Compare White Zinfandel with a dry rosé such as those from France.
For all of these, I've tried to pick the most obvious representations of the style to represent anchor points for you. Many good (even classic) wines fall between styles or are less obvious examples of a style. For example, the classic Riesling is an aromatic white, but it is certainly not aromatic to the degree of Gewürz or Viognier (and some could argue it partially belongs in the fresh/light category).
In a sense, these styles are like primary colors. Trying them allows you to taste other things and then think, in effect, "green...that's a little like yellow and a little like blue." Later, you can argue about the best shade of blue or admire complex patterns of multiple colors/shades. Indeed, I'm sure many wldg posters would criticize some of the wines on this list as being to "simple."
Beyond the specifics, I would just suggest that you be endlessly curious. If you see something on the shelf that you never heard of, consider buying it. The importer, distributor, and store purchasing manager all had to believe in the wine to put it on the shelf despite the lack of a ready-made market such as for Chardonnay or Cabernet (unless of course, it's there to target the market for cheap junk...just ask, most will say if you really shouldn't buy it).