Here's science that debunks old wives tales and counter-effective practices. This is from a Mexican cook named Bertha; I'm channeling her.

Mostly, we're talking about Mexican frijoles here, but many if not all principles apply beyong pinto beans. They apply also to black beans.

Principles

1. Use salt right off in cooking. Beans are not rendered tough by salt. In fact, a bean cooked without salt will never accept seasoning later—that ship has sailed.

   If the beans taste flat, it's because you salted at the end (or not enough).

2. If the beans never soften during cooking (after 4 hours), it's because they are too old. It's not you! Your only recourse is a pressure cooker. Buy your beans where they sell fast—a Mexican market or culturally similar store.
3. Soaking overnight gets water into beans before the pot heats. Presoaking can save an hour of time as well as energy (gas, electricity, etc.)
4. However, unpre-soaked beans will yield a richer broth (but...)
5. bis. If you drain the soaking water, some of that carries away the chemistry that causes gas.
6. Put no acid (tomatoes, limes, lemons, vinegar, salsa, etc.). It's one reason beans wiil remain solid for hours. The acid closes holes in the bean skin. Tomato goes into charros only at the end, lime only at the table:

   Salt from the start, acid at the end.
   Say it twice and
   you'll never make a hard pot again.

7. The pot must whisper (simmer only), not boil, lid slightly off! High temperature slams the beans against the pot, tears their skins, splits them open, and the beans dump their stach and turn the pot to mush before the centers have cooked—split and mushy pot.

   If the beans became tasteless mush, the flame was too hot.

   If fond is produced at the pot's bottom, that's not a mistake (as long as it's nit burned). It's flavor.

8. A Mexican pot has a big spoonful of fat (manteca or other) in the water from the very beginning and not at the end. Fat carries flavor in ways water cannot. (Cf. spice blooming in Indian cooking.) Fat turns the bean water into caldo de frijol. Also:
   • ½ onion (in one piece)
   • 3 whole cloves garlic
   • sprig of epazote (last ½ hour)
   • bay leaf (good, but no replacement)

9. Never pour out the broth!!!

   That broth is the black gold that you are cheated out of. It's the flavor. It's what makes the refritos creamy. It's what you freeze the beans in so they do not dry into pebbles.

   Always freeze and/or store beans in their broth. Its absence is what makes factory cans crap.

   Canned beans are beans whose biography has been removed.

   Last, a can of beans can save dinner, last minute. What is left out, though, is onion, garlic, manteca, epazote and broth.

Economy: The week starting with Sunday dinner!

Sunday	pot of beans in their broth with diced onion and cilantro.
Monday	refritos friend in manteca.
Tuesday	tostadas.
Wednesday	charros with bacon and tomato.
Thursday	the last of it puréed into soup with crema and thin tortilla strips.