Decide on How Much to Spend. Your research should give you some idea of how much an item costs. Some products, like olive oil and chocolate, have different price categories. Know what you are going to use the item for and what quality you need. You probably would want to buy olive oil in a higher price category (say around $30) if you are using it to drizzle over warm slices of ciabatta or tomatoes and mozzarella. A lower priced selection, however, would be much more suitable if you were planning to saute with it.
Read the Label. There are several important facts you can get from the label. Make sure what it says on the front matches what's on the ingredient label. If you're buying hazelnut oil, the ingredient label should say something about hazelnuts. Even products from foreign countries should have ingredient labels in English. However, this rule does not seem to be enforced too strictly.
Very important is the expiration date. Certain specialty items don't move very quickly on the shelf and may be past their expiration date. A reputable gourmet store will remove these items when expired. If you find more than one or two expired items, find a new place to shop.