In a medium (heavy-bottomed) saucepan, add the prepared berried or fruit, and add sugar, salt, and lemon juice. Stir to combine. Bring to a boil and boil for about 20 minutes.
Stir the mixture as it boils so that it thickens evenly and doesn't burn on the bottom. Adjust the heat if it's boiling too vigorously but don't let it stop boiling.
When the jam is done, turn off the heat and remove the pot from the heat. Transfer the jam to the jars (carefully, because it's hot!) and allow it to cool at room temperature.