How can I choose good avocados at the supermarket?

Depends on if you'll buy for instant consumption or for storage.

If you want to eat/prepare them right away, you want an avocado that feels soft on the inside, when pressing them they will cede and have that soft feeling ripe avocado has. It shouldn't cede very much though, as those are past their prime. The very good ones even smell in a nice avocadoey way a bit (or maybe that's just my insanity.)

If you want to prepare them later, you want firm ones that cede only a tiny little bit (the rock hard ones mostly never ripen in my experience,) you then store them in a porous bag (the typical brown paper bag or a newspaper) to let them ripe. To speed up the ripening, you can add an apple to the bag.

See also this related question

Avocados don't ripen until picked, so you may find under-ripe ones in the store; these will be hard and bright green. You can allow them to ripen at home quickly by placing them in a paper bag and sealing it. Already ripened avocados will have a bit of give to them when squeezed, without being too hard or too soft. They'll also be dark green to green-black in color.

Your best bet is to plan ahead and purchase the firmer ones and allow them to ripen at home. If they're ripe before you need to use them, refrigeration at that point will extend the life. If you're not using the whole thing at once, then use the side without the pit first. Leave the pit in the other half and give it a quick shot of vegetable spray (pan coating) and then cover with plastic wrap before refrigerating.

Plastic wrap alone is still porous and will allow the avocado to oxidize and brown. Spraying with veg. spray first will help to coat the surface and protect against browning.

If you can squish a avocado in your hand, it's much too ripe. Everyone else has had a squish of this avocado, and it's been manhandled.

Depending on the variety in your supermarket (In Australia, we usually get Hass Avocados, which go from a green colour to a black colour), you want one that's still firm when you buy it, and after a few days in the fruitbowl with the apples, it will become a nice constancy: still not completely soft to touch, but you can't play football with the thing anymore.

Give it a good mush with the lemon/lime/sour cream, and that avo is ready to become a GUACAMOLE!

A perfect avocado will be firm but not hard, and will not be squishy at the stem end. It will smell good, and the skin will be an even color all over.

I got this from Rick Bayless's TV show recently: A fully ripe avocado will give when you press on the end opposite the stem. The flesh ripens/softens from the stem down, so if the end farthest from the stem gives when pressed, you can be assured the rest is at least as ripe.

As to how soft it should be? Well, that's up to you. Buy one that's soft on the end, and cut into it as soon as you get home. See if that's too soft or not soft enough. Try to remember how it worked out for you the next time you buy. Eventually you'll get a sense of how you like them.

Things to look for in an avocado:

• Make sure it has the little nub of stem still on it. If that's missing, that end will likely be all brown under the skin.
• It should give when pressed, but should not feel like it's loose inside the skin.
• Avoid ones with places that are significantly softer than the rest of the avocado.
• Avoid ones with cuts in the skin.
• Avoid ones that have obvious bruising or discolored areas in the skin.

The easiest way to know that an avocado is ripe is by how easy it peels. Unfortunately, you can't do that at the store. Color and firmness are good indicators of ripeness, but a bit less reliable. In my own opinion, I'd prefer to get avocados I know are unripened and ripen myself instead of risk buying overripe avocados.

There are a few things you can do to get ripe avocados fast:

1. As luls mentions, place them in a paper bag. The trapped ethylene gas will cause faster ripening.
2. If they are very unripened, throw a ripe tomato in the bag as well. The extra ethylene gas will only help to ripen the avocado quicker.

Press lightly near the stem. If it gives to the touch, but doesn't give anywhere else, it's a keeper. If it doesn't give at all near the stem, it needs more time.

Someone taught me a method that hasn't failed me yet: the "reverse turkey-timer" (as I call it).

You could gently squeeze an avocado to see if it's soft, but I think you're more likely to feel bruising than ripeness. Other shoppers (like you!) could have damaged it with aggressive squeeze-testing, and unless you have the luxury of local fruit (it's a berry!), it may have been banged around in transit.

The method I use is to push the stem (gently!) into the avocado with your thumb. See how much resistance it gives. If it yields easily, it's ripe. In the process, you should see a bit of the flesh if the stem pushes in. If it's over-ripe, it'll be brownish.

Some posts say you should try removing the stem. This may be valid, but I think it's too destructive a test. It leave your grocer with produce which a) others cannot test in this way and b) is susceptible to rot.

Here is how I tell (in the store) if an Avocado is worth buying or not. I pick up the avocado in my hand, and squeeze it, but only gently. I'm looking for an avocado that is firm; it shouldn't be too soft or too hard.

As a test for the kind of firmness we're looking for, take your thumb of your left hand and with it, touch your pinky finger of the same hand (your thumb and pinky should be touching). Take your other hand, using your index finger, feel the muscle on your palm under your thumb. There should be a little give when you push it. Now squeeze your pinky and thumb together really tight! Feel your muscle again. That is the kind of firmness we are looking for.

The avocado flesh should give when you poke it when and apply a decent amount of pressure. You'll soon learn when soft is too soft, and when hard is too hard. It just takes some practice!

Unless you are very lucky, it is almost impossible to find ripe avocados at the store. I buy 4-5 at a time and let them ripen on the kitchen counter.

When they are ripe, I store them in a zip-lock bag in the salad drawer of the refrigerator. They will keep for 1-2 weeks, but continue to ripen slowly. Eventually, they will go "bad".