When you want to grow bean sprouts for salad or for the beans after harvest, germinating the beans is a very simple process. There are some things to keep an eye on, little things that go unnoticed to the naked eye that could prevent the beans from growing into a healthy plant.
First thing is to get a batch of beans from your chosen variety. Make sure to get fresh beans, harvested the same or previous year you'll be planting them, as they make for stronger plants and more nutritious sprouts.
One of the most common things that prevent the bean from germinating correctly is a cracked shell. This happens when the beans are over dried for storage or from damage at harvest.
One simple way to detect beans with cracked shells is to soak them for about 30 minutes to 1 hour. If the bean's shell is damaged, it will start swelling and separating from the bean itself, this is caused because the inside of the bean absorbs water much slower, causing the extra water pressure of the shell to loosen it and sometimes causing the bean to take a "popped" shape, kinda like popcorn.
Seed with a healthy shell will not swell or even feel softer at all. The bean's "eye" is where the new plant takes water, and as it softens it's food storage, some will get into the coat making it adjust to the extra volume. This happens in about 12 to 24 hours after contact with moisture, and this is a sign that the plant is getting ready to germinate.
Depending on what you are looking for in a bean, you could select the biggest seeds, the most uniform in shape, or the best tasting (you'll need a few batches from different sources to tell which ones are tastier) to germinate.
In general any food grade bean should be able to germinate, but you will sometimes get really old or damaged seeds in the market. Those beans are kept in stores because they don't lose their nutritional value when cooked, but are no good for germinating, as the bean embryo dries and dies.
I've personally had problems with temperature when germinating beans, but choosing only the best beans ensures only the best plants and sprouts. Have fun Growing Beans!