Rinse seeds or beans well and drain. Put them in four parts lukewarm water and soak overnight in a dark place for six hours, and up to 12 hours for the tough-skinned beans.
In the morning you'll probably see gas bubbles. Pour off the soaking water and use it to water your houseplants; it's full of minerals. Rinse the seeds in cool water for a few minutes and remove the duds that float or they'll attract mold. Now spread the seeds evenly in your sprouting container and leave them in a dark place where they can drain but stay moist and get some air.
For a simple sprouting container, poke tiny holes in the bottom of a plastic bag. Put the seeds inside and lay a folded, wet dishcloth over them. Put the open bag in a colander set over a bowl.
Or reuse the plastic box alfalfa sprouts come in: Poke holes in the bottom of the container, replace the foam pad and put the seeds on top. Replace the lid. Yet another method is to spread the seeds in a bisque container sitting in a half-inch of water. Unglazed pottery absorbs water, keeping the walls moist.
Rinse the seeds frequently with cool water. Ideally this means every four hours; realistically, most home-sprouters do it once in the morning and at the end of the day, and once at midday when possible. Shower the seeds (through the towel if you're using one) with a light rain for a couple of minutes and let them drain completely. They'll grow bigger and fatter if they're not shaken up too much.
Most seeds will show tiny tails in two to three days. Lentil, azuki, mung, green pea, peanut, barley, wheat, garbanzo and sesame can all be harvested at this point. They are delicious tossed into soups and salads or lightly steamed and eaten with a touch of sesame oil or butter. Try tossing a mixture of them with some dried seaweed and sesame oil for a super-nutritious salad. Of course, you can wait and let your sprouts grow, tasting every day to see how you like them. Sesame and sunflower grow bitter when long; wheat and other grasses grow sweeter. Leafy sprouts can be placed in indirect sunlight the last day before harvest to develop chlorophyll.
To harvest, immerse your sprouts in cold water, shake lightly, and pull any hulls or unsprouted seeds that float up. Drain thoroughly, put in a plastic bag, seal and refrigerate. Sprouts will keep about a week in the refrigerator, where they will continue to grow slowly. (Supermarket sprouts wilt sooner because they are usually older when you buy them.)
A good portable system for backpacking or boating is to use a plastic bag with tiny holes in the bottom, put a damp cloth on top of the seeds, put it inside another plastic bag and seal both together. Rinse regularly and hang the bags anywhere handy to drain.