How do you choose a good olive oil in a supermarket?

The olive oil shelf is a wall of rustic labels, cheerful farmhouses and words like "premium" and "traditional", which mean whatever the marketing team wants them to mean. The useful information is in smaller print. Here is what we read, in order.

1. The grade: extra virgin

Olive oil grades are defined by standards, not by vibes. The International Olive Council, the intergovernmental body for olive oil, sets out the grades: extra virgin is the top category of virgin oil, with a free acidity of no more than 0.8 grams per 100 grams. Virgin olive oil is allowed up to 2 grams. Plain "olive oil" is a blend of refined olive oil with some virgin oil, and refined oil is made by refining virgin oils.

What that means in the aisle:

• Extra virgin is the one to choose when you want to taste the oil: dressing, finishing, dipping bread.
• "Olive oil" or "pure olive oil" is milder and works for everyday cooking where the oil is not the point.
• "Light", in our experience, describes a milder flavour and paler colour. Read the grade beside it.

Acidity is a lab measure, not something you taste as sourness, so a bottle shouting "low acidity" is telling you something technical rather than something about flavour.

2. The date

Olive oil is not wine. In our experience its fresh, grassy character fades with time rather than deepening. We look for a harvest date (sometimes shown as a season, such as a two-year span) and pick the most recent one on the shelf. Not every bottle shows it. If there is only a best-before date, the further away it is, the fresher the oil is likely to be.

Fresher stock sometimes hides at the back of the shelf. Rummaging is permitted.

3. The origin

A label that names a single country, region or estate is giving you more information than one that says the oil is a blend from several countries. Neither is automatically better, and blends can be pleasant and good value. But specificity is a sign that somebody is willing to be held to something.

Bottles carrying an official protected-origin logo and a named place tend to cost more and can be lovely; they are a treat, not a requirement.

4. The container

We treat oil as something that prefers a cool, dark life. We prefer dark glass or a tin over clear glass, and we avoid bottles displayed under bright shop lights or next to a warm window if there is a choice. At home, the same logic applies: a cupboard away from the stove, cap on.

5. Your own mouth

Labels get you to a shortlist; tasting gets you the answer. Buy two extra virgin oils at a price you would pay again, pour a little of each into a spoon or onto plain bread, and compare.

• Fruity: smells of green apple, cut grass, tomato leaf, artichoke, or riper notes like almond.
• Bitter: a pleasant green bitterness on the tongue.
• Peppery: a tickle or catch at the back of the throat. Coughing a bit is a compliment.

What you do not want: smells of crayons, wet cardboard, vinegar, or musty cellars. Those suggest an old or damaged oil.

A sensible two-bottle system

Most kitchens are well served by one reasonably priced oil for cooking and one extra virgin oil you love for raw use. Spend the money where you can taste it.