Salad dressings-- depends on what kind your are making:
- When there other strong flavors in play, use your grocery store extra virgin.
- If it's only oil and vinegar, use one of your best extra virgin and let the olive taste shine through.
Dipping -- Use your very best, like Prato Lungo. We buy special bottles based on recommendations, like you would with wine. For example, we bought a bottle from the olive oil section when we were at Eataly in NYC.
Baking -- Use canola, or the flavorless version of olive oil which is available in most grocery stores.
Frying - Use something like a canola, soy or peanut oil, i.e., a cheap, flavorless oil that has a high smoke point.
When in doubt, taste and trust your instincts. Use it to compliment or enhance the flavors of what you are making.
There is only one no-no in using olive oil. Don't waste the extra virgin olive oil in situations with heat, like sauteing.
I hope this is helpful, Jane.