If you are interested in jams and jellies, many low-sugar recipes are included in the Slim Set or MCP reduced sugar pectin packages. Fresh berries, of course, come from your own back yard, roadside stands in season, perhaps neighbors, or perhaps wild if you are lucky like blackberries in Oregon. We utilize all sources. Store your sealed fruit in a cool dark place. This is the standard advice, although I canned during the three years we lived in Hawaii, and the fruit lasted ok, although for a shorter time.
Vegetables are another problem.
They must be carefully preserved by a different method for safety. Again, find your State Extension Service and you will get all the help you need. We do a lot of canning ourselves. One of the best resources I have found is a book put out by the people who make the canning jars, Kerr. It talks about home canning and how to freeze foods.