Buy in season as much as possible, out of season fruit will either taste funny because it was forced to grow in the wrong climate, or will be old because it was shipped half way around the world. A good guide to what's in season is Romany's writeup below. Also, don't buy just because the price is low, fruit is perishable and low prices probably mean old fruit. Along the same lines, only buy what you need -- letting fruit rot in your refrigerator is like throwing your money away.

These are only fruits that I know about personally, so the list isn't even nearly complete. If you know about othes, node them!

Apples: Bruises are the biggest fault with apples; they are hard to see but have a horrible texture to accidentally bite into. Before buying an apple feel it all over for soft spots. If there's any doubt whether there is or isn't a soft spot, put it back. Also, a generally soft texture might mean the apple will be meally. Also keep an eye out for any holes in the skin surface -- who knows how they got there or how deep they go. Discolorations are part of some apples' natural appearance, if the texture of the colored areas is the same as the rest of the apple, it's probably fine.

Bananas: Well, first make sure you're not buying plantains, or you're in for a nasty surprise. Next, look at the coloring. Green means under-ripe, and the fruit will be hard to peel and not taste very good. Green ones will ripen if left at room temperature for a few days. Yellow, or yellow with some black areas means ripe, the perfect banana. The more black is visible, the lower will be the quality of the fruit, so avoid "well done" looking ones.

Berries: In my area, blueberries, raspberries, and blackberries all come in closed plastic boxes. Since you can't feel the fruit, you'll just have to go by appearance. Fortunately, since the individual fruits are so small, damage is usually quite easy to see. Remember that if you can see one bad fruit from the outside, there are probably more on the inside. Shriveled or mangled berries of any kind are bad, and berry juice coming out of the box is a bad sign. Also, look for mold through the bottom of the box, it starts forming really fast after berries have gone bad. Uniformity of color is a good sign. If you can force open a corner of the box to get a berry to taste, do so -- the store won't mind as long as you end up buying fruit.

Cantaloupes (Muskmelon): Make sure that no stem remains, if the stem scar looks torn then the fruit was probably picked before it was ripe. All of the netting on the melon should be thick and have a texture like cork, while the skin underneath should be yellowish rather than green.

Citrus Fruit: Oranges, lemons, grapefruit, etc. Skin color of citrus fruits means nothing, so don't try to judge them by it. Instead, try to find a fruit that is soft to the touch and feels heavy for its weight. This indicates that it will be ripe and juicy, and sweet if it's a sweet citrus. If any of the fruit's skin is withered or wrinkled, its time has passed. Dull, dry skin is also evidence of excess aging, only in a dry climate rather than a humid one.

Cherries: Well, the really easy way to tell is to just eat one of each kind. Ooh, shoplifting, but again the store probably won't care if you actually buy some cherries. I know it seems like a pain, but inspect each individual cherry instead of grabbing a handful. When I look through cherries, two thirds of them are mushy, cut, leaking, or otherwise dysfunctional. With the kind of prices they charge for this fruit, it's very much in your interest to get the best ones.

Grapes: Bad grapes will be squishy or even wrinkled, avoid them. Good grapes are firm and reasonably well attached to the stem, avoid a bunch of grapes that have a lot of fruit missing. If in doubt, just eat one. Check the produce sign to make sure they don't have seeds, if you care. It sucks terribly to chomp into what looks like the worlds yummiest grape and hit a bitter seed.

Peaches, Apricots, Plums, etc.: My mom taught me the rule for choosing this kind of fruit. Feel the tip of your nose, get an idea of how firm it is and how much give it has. The fleshy sunken area that surrounds the fruit's stem should have the same consistency. If it's softer, the fruit is over-ripe. If harder, the fruit is under-ripe. This method hasn't failed me yet, and guarantees a great fruit experience. As always, look out for bruises and holes in the skin, and avoid wrinkled/shriveled fruit.

Pears: Fitch tells me in a /msg that pears can be chosen by pinching them near the neck. If they're soft there then they are either ripe, or will be soon.

Rhubarb: Rhubarb is not a fruit, people!

Strawberries: Don't fall for strawberries in a box/flat, they won't be as good as hand-chosen ones. Pick uniformly red strawberries, and select the smallest ones you can find. Make sure the stem cap/leaf part hasn't fallen off, if it has the strawberry is too old. Discolored and uncolored areas mean a young fruit, and strawberries won't ripen once harvested. Mushy, brown-red areas are bad, and will have to be cut off before the strawberry is eaten. As with berries, mold grows and spreads fast on decayed strawberries, so look for it.

Watermelon: Ack, there's no good way to buy a watermelon unless it's already cut. If it is, buy it if it has dark seeds, or white seeds if it's a seedless variety. Any pale or white flesh will not taste good, so buy a melon with as little of that as possible. Stringy, dry flesh means the melon is too old, and was probably aged after harvest. Yellow watermelon (yes, these exist) are rare, and are often only available from vendors who know what's up. They're also delicious, and have even more sweetness and watermelon taste than their red cousins. I've never been able to fathom why they aren't more popular, it must be an aesthetic thing.