Saving your own seeds is one of the easiest things you can do to live more sustainably. We save the seeds from all of our organic fruits and vegetables. It's not worth the effort to harvest and save the seeds from non-organic fruits and vegetables, simply because they usually don't sprout.
It's easiest to remove the seeds from the fruit or vegetable, rinse them off with purified water (reverse osmosis is ideal), then lay them out on towels to dry (the towels or paper towels will help to absorb the initial moisture so they don't mold).
Once they're dry, we transfer them to labeled mason jars for storage until we're ready to use them. I like the 4 oz jelly jars for most seeds, but I keep running out of them so I am also using some 8 oz jelly jars and pint size mason jars.
Brian sprouts our seeds in his hydroponic growing system to grow food hydroponically, but you can also sprout your seeds and grow them in dirt – indoors or outdoors.
Not only will saving seeds help you live more sustainably, it will help you reduce your food costs if you can grow your own food!