If the glass sides of the jar are slick as well, use another dish towel to help grip the jar.
If you can’t open the jar alone, have a friend hold the sides while you twist the lid.
If you’re having trouble inserting the spoon, try a few different spots around the lid.
You can buy duct tape at most grocery stores and hardware supply stores.
If your jar has a lot of condensation on it, wipe the jar dry before applying the duct tape.
If the lid is especially stubborn, have a friend hold the jar while you pull the handle with both hands. If the jar is slick, use a dishtowel to help you hold it steady.
Rotate the jar while running it under hot water to help distribute the heat.
If the lid is still stuck, cover it with a rubber glove or a dish towel before trying again. This will help pry the lid loose by adding friction.