An old mechanic's trick -- you can magnetize a screwdriver by rubbing it with a magnet. Makes it worlds easier to pick up and install tiny, easily lost steel screws. They'll stay on the end of the screwdriver due to the magnetism. You rub the magnet down the length of the screwdriver to magnetize it. It works best if you have the polarity of the magnet (plus to minus, north to south) lined up with the length of the screwdriver, and you rub in one direction only. After each swipe lift the magnet away from the screwdriver before you make the next swipe. You'll find the screwdriver will stay magnetized for a very long time.
Sometimes having your screwdriver magnetized can be a pain. In that case you can de-magnetize it by rubbing it the opposite direction.
There is a tiny metal clip that holds the camera down on my iPhone 3GS. It fell out after I had removed the screw that holds the camera in place, as directed. Only intuition and good luck allowed me to figure out where it had come from.
I also found out that the connector for my camera came loose from the BACK of the logic board. it snapped back in place, no problem, but I could have easily tried reassembling the phone without it connected, and either found things didn't want to fit, or ended up without a functioning camera, and a panic attack that I had clumsily destroyed same.