Gather ingredients: fruit, sugar, lemon juice (or lemon), pectin (if needed)
Wash and prepare fruit (peel if desired, remove pits/seeds, chop)
Crush fruit to desired texture
Measure fruit and sugar accurately
Add fruit to a large pot
Add lemon juice
Stir in sugar (and pectin if using)
Bring mixture to a boil over medium-high heat
Boil steadily until it reaches the gel point (about 220°F/104°C, or passes a plate test)
Skim off foam if needed
Remove from heat
Ladle hot jam into sterilized jars, leaving appropriate headspace
Wipe jar rims clean
Seal with lids
Process jars in a boiling water bath (if doing shelf-stable canning) for the recommended time for your jar size and altitude
Cool jars undisturbed until set
Check seals; refrigerate any unsealed jars
Label and store in a cool, dark place