Fill your canning pot with enough water to cover the jars you are using, and begin to bring it up to a boil.

Wash your jelly jars with hot soapy water, rinse well, and place them in the pre-heating canner to warm and sanitize the jars (this isn't necessary, but you do need to preheat the jars and I find this is the easiest way).

Sift the powdered pectin into the granulated sugar to remove any lumps.

Whisk the dry ingredients together until well-combined.

Pour the juice, and any additional acid that you may be adding, into your jelly pot.

Heat the juice to a rolling boil over medium heat, stirring and watching so that it doesn't boil over.

Remove juice from the heat, and pour in the sugar and pectin mixture.

Stir until the sugar is dissolved and all is well mixed.

If you are using the plate test method to check your jelly, put a few small heat-resistant saucers or ramekins into the freezer to chill.

Return the pot to the heat, and bring back up to a boil.

Boil the mixture hard, watching it carefully so and stirring so that it does not scorch or boil over. It will foam up quite a bit, which is why you want a larger pot!

Cook your jelly until it reaches 220 degrees F, or do a plate test to check for gelling.

Plate test: take a cold saucer out of the freezer. Drop a half teaspoon or so of hot jelly onto the cold plate. Let it sit for a few seconds, then run your finger through the center of the blob.

If the jelly has set, a clear line will remain down the center. If it quickly runs back together, you need to boil it a bit longer. Let it simmer for a few more minutes and check it again. Repeat until you get a good set. Remember that the jelly will be runny until it cools and sets!

Wipe the rims of the jars with a clean, lint free cloth dipped in hot water or distilled vinegar. Make sure the rims are clean before placing your lids and rings so that you get a good seal. Clean jar rims mean safe seals!

Place your canning lids on the jars and secure with rings. Do not overtighten the bands on the jars. They should be lightly snug, or "finger-tight". You want to keep the liquid in while processing, but allow air to escape.

Using a jar rack or jar tongs, carefully place the jelly jars into your boiling water bath. Make sure there are 1-2" of water to cover and room for a vigorous boil. If you stack jars, use a metal divider to protect the jars from breakage.

Cover the pot and bring back up to a rolling boil. Once the pot is boiling, set your processing timer.

Carefully remove the jars from the canner and set them aside to cool. Do not place hot jars on a cold metal or stone surface or they may crack. Let them cool on wire racks or thick kitchen towels.

Leave undisturbed for about 12-24 hours. Do not adjust the tension on the bands before the jars are completely cool (unless you are using reusable lids- then follow manufacturer directions to tighten bands immediately after processing while jars are hot).