Green bean seeds are some of the easiest seeds to save, and the International Seed Saving Institute recommends them for gardeners who are just beginning to practice seed-saving. If you have a crop of green beans from non-hybrid seeds, try saving some for your next planting. Hybrid seeds have been bred to produce a better crop, but may not breed and produce a successful crop from their harvested seeds. If you still have your seed packet, check to see if they say "hybrid" on the label, or speak to a worker where you purchased your seeds.
Open healthy bean pods and remove the seeds when they are brown and dry. This should be about four to six weeks after you harvest beans for eating.
Place the seeds in a plastic bag, and put them in the freezer for 48 hours. This will kill insect eggs that could be on the seeds.
Remove the seeds from the freezer after 48 hours, but do not remove them from the plastic bag until they have thawed to room temperature.
Place the room-temperature seeds on paper plates or paper toweling, and allow them to air-dry for 48 hours. Roll them around periodically so air can get to all sides of them.
Place the dry seeds in an airtight container, and store the container in a cool, dark place until you're ready to use the seeds.