The best handover is useful when the person who wrote it is unavailable
A handover can be a long document that nobody reads or a short note missing the one detail someone needs. Useful instructions need enough context to explain the task without assuming the next person already knows the usual shortcuts. Where do you draw that line? A list of current work, deadlines, contacts, and the location of essential files seems like a good foundation. It also helps to mark what is uncertain rather than making everything sound settled. What would you want to find on your first morning covering another person's responsibilities?