If you're called away from the cooker - by the phone, say, or by someone at the door - take pans off the heat. It's the easiest thing in the world to forget about them.
Keep electrical leads from trailing over or going near the cooker.
Wash fruit thoroughly. Crush. Add lemon juice. Add grated rind of 1/2 lemon. Add sugar. Mix thoroughly. Heat rapidly to full rolling boil. Stir constantly before and while boiling. Boil hard 2 minutes. Remove from fire and stir in fruit pectin. Skim. The Household Searchlight