Combine the ingredients according to the texture you want: For a smooth jam, cook the fruit with 1/4 cup of water and then add the sugar and lemon juice. For a chunkier result, toss together the night before cooking. The fruit will maintain its shape during the process. Add all to the pot and cook immediately if you'd like some large bits of fruit.
Once you have the fruit, sugar and acid in the pot you will need to cook it down over medium heat, stirring constantly, until you reach the jell stage. You will know you are getting close when the bubbles in the pot get big and lazy. Then there are three tests you can do–use all three to get jam that is just right:
Temperature–Jam reaches jell stage at 220° F., so dunk a candy thermometer down into the pot. Keep in mind, however, that the temperature may vary throughout the jam pot so be sure to stir constantly to get a good measurement.
Sheeting–Lift a jam-coated wooden spoon out of the pot sideways. When the jam is thin, it will dribble off in a stream. As it thickens, it will come off in drips. When it reaches the jell stage, the jam will come off in sheets–two drops will unite and fall in the pot as one.
Freezer–A few drops of jam on a frozen plate or the bottom of an ice cream container will wrinkle when you push the cooled puddle with your finger.
Once you have reached the jell stage, remove the jam from the heat and stir for about five minutes, to release trapped air. Refrigerate, covered, for up to three weeks or can, using the boiling-water method, and store for up to one year.