Select a suitable jar. You can either use peanut butter or jam jars with plastic lids, or buy plastic lids for Mason jars.
Pound tiny holes through the lid. Make them close together and small--pound in as many as you can.
Fill the bottom inch or two of the jar with seeds you want to sprout. In addition to alfalfa or beans, you can use wheat grains, sunflower seeds, lentils, black-eyed peas and other seeds from plants used for food.
Fill the jar with water and let stand overnight.
Drain the jar in the morning by turning it upside down and letting the water drip into the sink. This is why you made so many holes--the faster the drainage, the shorter the amount of time you have to stand there holding your jar.
Add more water, gently shake the jar and then drain it. Set the jar in a windowsill with a lot of sun. Repeat the process of adding, shaking and draining two or three times a day. Seeds should sprout within a few days and are ready to eat when the shoot is at least as big as the seed.