Locate the healthiest green bean plants in the garden. Plants that do not contain diseases or damages will produce the most viable seeds.
Allow the green beans to remain on the plants until they turn brown. They are ready for harvest when the seeds rattle inside the pods.
Remove the green beans from the vine. Place them on a newspaper in a warm room. Allow the beans to dry for an additional two weeks to eliminate any remaining moisture.
Open the pods by pressing on them slightly. Remove the bean seeds inside. Place them in a bowl, and then remove any pod material from the seeds.
Place the green bean seeds inside an envelope. Place the sealed envelope inside an airtight jar. Store the jar in a dry and cool location.