I discovered this years ago and have been buying my preserving jars at the local hardware store ever since. Not only are the jars I want readily available, they're cheaper and if the stock runs out, the folks who run this main street business will happily order in more ~ in any season. Just a word to the wise.
So, of course you need some of these preserving jars to bottle up your jam, jelly, or relishes. I use the 250 ml. or 1 cup size for jam. Those with big families may wish to use the next size up, which is 500 ml or 2 cups. At the same time, elderly couples or people on their own may wish to use the "jelly jar" size. At 125 mls or half cup, this size is easier to use up before the stuff inside goes funky. But you'll also want to get some bigger jars so you can make gifts of the rest of the batch if you wish. ;o)
Wash the jars you choose in hot, soapy water, rinse thoroughly, wipe the rims with a clean dish cloth and place, on their bottoms, on a clean cookie sheet in the oven. Turn the oven on to 250 degrees when you're almost ready to cook the preserves. It only takes my oven a few minutes to heat up and I cook my jars for 20 mins. Judge accordingly.
The lids are also washed in that hot soapy water and rinsed well. Then place them, rubber rings up, into a large Pyrex glass bowl, along with a preserving funnel, tongs, metal ladle, and a couple of spoons. ALWAYS ready a couple more jars and a few more lids than you're expecting to use. Doo-doo happens sometimes and you want to be prepared for it.
You also need a kettle for boiling water to sterilize those lids, and a clean, sterilized cloth for wiping the jar rims. I just bleach the cloth I use first in a light bleach solution (water and bleach), then wring it out, fold it and set it on the hot stove to the kettle for the water. Of course you need a very large saucepan or preserving kettle for your preserves.