Garden crops can be classified as either dry fruited or wet fruited. Collecting seeds from dry fruited crops, can be as simple as going out to the garden, handpicking a few mature seedpods, and bringing them into the house for further drying and cleaning. Fruits from wet fruited crops must be picked when their seeds are mature. The harvested fruits (squash, melons, etc) are either crushed or cut open, and the seeds are extracted from the flesh and pulp before the seeds are dried. Be sure to plant any heirloom or open pollinated seed varieties, hybrids make for some fun growing in the garden, but saving seeds from hybrid plants can result in either non-viable seed or can revert back to one of its parents and sometimes what you planted will come up as a totally different plant.
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You can opt to store in the fridge if you have space 32-41°F❄can be ideal for long term storage. However, it isn’t necessary! Any cool, temperate, dry location is suitable for storing seeds. Inside a closet, or in a cool basement are all excellent choices. The location doesn’t need to be pitch black per se, but seeds should be stored out of direct sunlight. As opposed to an expiration date, you’ll most often see “packed for” date on garden seed packages – such as packed for 2018. Don’t throw out or avoid planting seeds if you don’t use them by that date! The date represents when they were last tested for germination rate, and the minimum germ rates in the US are quite high! Often seed packed from a few years ago will sprout just fine.