I agree with Laura and would add that my first hint is to look for the telltale wrinkled beans that seem to never absorb water no matter the soak. I use baking soda when I cook garbanzos for hummus (it allows their skins to magically separate from the bean resulting the most amazingly smooth hummus!) and I'll give it a try for the elderly beans I might encounter.

Elderly beans sometimes never cook. If you've had the beans for a long time--that might be the problem.

Agree with what everyone says! And when I have trouble with my beans it is because they were not fresh. I always buy dried beans bulk in a place that has high turnover.

Here's a pretty definitive link that appears to cover all bases: to pre-soak or not, to add baking soda or not (not), to salt early or not (not). http://ruhlman.com/2011/03/how-to-cook-dried-beans/

Did you cook the bean just in water? Adding tomatoes or any other acid before the beans are soft will instantly stop them from softening further, no matter how long you cook them. ;o)

So sorry! Sometimes even long-soaked beans just won't soften up. Sometimes a pinch (just a pinch!) of baking soda does the trick.

It sounds like your last batch of beans didn't turn out as well as you'd hoped. For the next batch you might want to check out some of our bean cooking strategies: https://food52.com/blog/4634-how-to-cook-dried-beans