Image from Wikipedia.
Before you soak dry beans, pick them over to get out little rocks, dirt clumps, and anything else that shouldn't be there.
Put them in a strainer and rinse them well, until the water runs clear.
The day before you want to cook your dry beans, put them in for a soak. Soaking helps reduce the discomfort that some people feel after eating beans, and it also helps them cook faster.
Put your beans in a bowl or pot, and cover them with twice as much water. Leave overnight, anywhere from 8 to 36 hours. If you don't like the thought of leaving them out on the counter, you can put them in the fridge.
Pour your beans into a strainer and rinse well, until the water runs clear. Put in a pot big enough to be no more than 2/3 full, then add your beans and twice as much water. I like to use a heavy pot, such as a Dutch oven, because it insulates so well that I can turn the heat on the stove down to almost nothing. It also helps keep the temperature even, so I don't have to check on them as often. If you see bubbles similar to soap bubbles, don't worry; it's normal.
Bring to a boil and simmer over low heat for an hour or two, until your beans are done. The cooking time may vary wildly, depending on the length of your soak, the hardness of your water, and the age and size of your beans.