Dry preserving these crops is essentially the same as saving them for seed. You can use the end product for either
feed (human or animal), or seed. This year I saved the seed from my snow peas (pisum sativum), and cowpeas (vigna unguiculata.) In both cases, I simply left the pods on the plant to dry. When they reach maturity, the pods and plants will die back and dry out. Some people believe that the drying plant helps dry the pods. I did it because it was relatively easy to harvest and shell the peas and beans after they were dry. The cowpea pods snapped off easily, while the snow peas took a bit more effort. Picking snow peas, or other p. sativum varieties seems easier when still green. Their pods seem to get really tough when dried. You can harvest any of the crops you mention while still green any time after reaching maturity. You can then provide a dry, well ventilated area for them to dry in. The key is the dry, well ventilated area. Also spread them out on a broad surface, such as a screen or cookie sheet. As long as the seeds have reached full maturity, you
should be able to save for seed from this technique. Either way you can get save seed for next year or keep preserved for eating. For storing, you can test whether or not the seeds are sufficiently dry. Dropping them on a hard surface, countertop, table, etc. should yield a sharp "clack" sound. If there is any hint of a dull thud, they are not dry
enough for storage. You can either store in paper or plastic. Storing in plastic has a tighter tolerance for dryness. The plastic won't breathe like paper and any excess moisture still in the seeds can lead to rot and mold. The sharp clack test will minimize any problems there. The upside of paper is its breathe-ability, which unfortunately is also its downside. You need to be more careful when selecting a place to store seeds in paper. A good compromise is wrapping the seed in paper then placing in a rigid, airtight, plastic or glass container. The paper and airspace acts as a buffer to help keep the seeds dry. A note about storing in plastic in a refrigerator: let the package return to room temperature before opening if you intend to only use a portion. Otherwise you inadvertently introduce moisture back into the seeds due to condensation. If that happens, you will need to re-dry them as described above. If you are saving for food purposes only and do not intend to save for seed, then you can use heat to speed the drying process. Placing seeds spread on a cookie sheet in a warm
oven will do the trick. When they reach the sharp clack point, take them out and let them cool before storage.