There are two schools of thought as to whether dried beans should be soaked in water for a while before cooking.
When you cook beans, the first part of what happens is the beans rehydrate themselves by drawing in water. The pre-soak or no pre-soak debate centres on whether it matters if this happens in the first hour or so of cooking in a pot of water, or whether it should happen on a kitchen counter in a vessel of water before cooking begins.
Soaking of dried beans is not necessary
The “not generally needed” school of thought can be said to be represented by Russ Parsons, the Los Angeles Times Food Editor. He says the only reason to soak beans is to reduce cooking time, and that otherwise, in his opinion, there’s no difference in flavour, texture or split versus unsplit beans during cooking. Parsons is backed, or inspired, by the Mexican food authority Diana Kennedy, who says, “If you want the best-flavored beans, don’t soak them overnight, but start cooking in hot water.” 
Parsons says that he finds that the taste of unsoaked beans is richer, and that they give off a richer, thicker broth, useful for some bean dishes. Some people believe that soaking beans overnight, and then discarding the soaking water, reduces flatulence, but Parsons says the science he’s seen says that you’d have to soak beans for up to 3 days for any of the flatulence-causing sugars to start to leech into the water, by which point the beans would be close to germinating. Some people believe that some of the nutrition also leeches out of the beans during a pre-soak, but there have been no studies done on this.
Parsons does acknowledge that pre-soaking reduces cooking time, and that older dried beans (any that you suspect are more than 6 months old), and tougher ones such as chickpeas, definitely require a pre-soak.
Parsons and Kennedy are not alone in their views. Many people say the best way to cook beans is through a long, slow cooking time, with no pre-soaking. This, however, could be seen to be at odds with today’s skyrocketing energy costs, the price of which after hours and hours of cooking can practically make those beans seem like caviar when the fuel bill arrives in the post.
Soaking of dried beans is necessary
This school of thought, which by the way is the traditional one in North America, holds that dried beans should be soaked in cold water overnight, or at a minimum, be subjected to a “quick soak.”
The main advantages are seen to be vastly reduced cooking times (from 1/3 to 1/2, depending on the bean, resulting in cheaper cooking costs), and more evenly cooked beans. Some believe the pre-soaking can also leech some of the flatulence-causing sugars out of the beans, making them easier to digest.
Bridget Lancaster of America’s Test Kitchen is an advocate of pre-soaking. In fact, she also recommends that there be salt in the soaking water (see separate entry on “Brining Beans.”)
The “soaker” school of thought also allows for a “quick soak” method. Here are two quick methods.
Quick soaking methods for beans
- In saucepan, cover beans with 2 inches (5 cm) of water. Bring to a boil, let boil for 2 minutes, let sit in the hot water for 1 hour.
- In saucepan, cover beans with 2 inches (5 cm) of water. Bring to a boil, let boil for 10 minutes, drain, cover again with 2 inches (5 cm) of water, let soak for 30 minutes.
For either quick method, make sure the dried beans you are using are relatively “fresh” dried beans (no more than 6 months old, including time on store shelf.) If you or the store have had them around for a year or more, they will need a full, long, proper soak.
If you’ve presoaked beans but then something occurs that you can’t proceed with cooking them right away, drain them, and pop them in a sealed container for a day or so in fridge, or freeze.
 Kennedy, Diana. “The Cuisines of Mexico.” Harper & Row: 1972.
Lancaster, Bridget. Learn to Cook: How to Brine Beans. America’s Test Kitchen. 25 April 2012. Retrieved July 2012 from http://www.youtube.com/watch?v=pRDL2C6M1_o
Parsons, Russ. Beans : To Soak or Not to Soak, It’s No Longer a Question. Los Angeles Times. 24 February 1994.
Parsons, Russ. Finally — it’s bean season. Los Angeles: Los Angeles Times. 27 October 2011.