Saving seed of open pollinated (non hybrid) seeds is easy.
1)Pick seed from healthy, mature fruit.
2)Dry on butcher paper.
3)When dry, put the seeds in a jar, and sprinkle a little diatomaceous earth on top.
4)Put the lid on and set in the refrigerator until next season.
NOTE: For sticky seeds like tomato, put the seed in a strainer and blast with water until the seeds are clean. Let them dry on a non stick surface. Then follow steps 3 and 4.