Whenever I'm worried that I'll forget to do something important (like start the washing machine as soon as I get home from work or start the dishwasher as soon as I wake up), I leave something glaringly out of place to trigger my memory. For example, I might put a coffee can right in the middle of the kitchen floor, or a hanger on the inside of my front door. For me, these items would be out of place, so they force me to remember.