In reply to FrankBooth:
My personal 'golden rule is:
You can never cook too may Roast Potatoes!
Seriously, if you are cooking a roast dinner, all of the potatoes will get eaten no matter how many you do, and despite reminding her pretty much every time I go back home, my Mum still seems to forget this rule.
Gloves is another good one, I seem to be constantly losing single gloves and have an entire Drawer full of odd gloves.
Micro-usb cables is another biggie for me.
Guidebooks.