I've taken to putting my keys, change, wallet, pen, etc.. into small Ziploc bag and sticking that in the plastic tray. Mobile phones and other electronics go in a back pack or Laptop case. At LHR/EWR/IAH/CDG/SIN the ziploc bag never gets more than a cursory look and I don't let go of the tray until I'm about to pass through the metal detector. It's proven to be a very handy solution if you have multiple sets of keys or currencies. More often than not the backpack doesn't warrant a search either (even post 9/11). Laptops...well that's a whole other story...