Need to replace your trusty old level? You can check it for accuracy. Lay one working edge on a flat surface and check the bubble. Swap it end for end, then check the bubble again. It should be in the same position. Now try the opposite working edge. Take a reading, switch end for end, and take another reading. The bubble should be in the same position. Likewise check for plumb by holding it against a flat vertical surface.
Magnetic tipped screwdrivers are handy for keeping a hold on smaller screws, especially in tight places where your hands can't reach. You can magnetize your screwdrivers by rubbing a magnet down the blade five or six times in only one direction. To demagnetize, rub the magnet in the opposite direction.
It seems that for some jobs, you need three hands to get it done. Your pliers can lend you that extra hand. Use the pliers to grip the wire or small piece you need to have held. Then wrap a rubber band around the handles to maintain the grip while you complete the work.
Don't rely on eyeball measurements alone as sight lines can often be deceiving. Take a few seconds and use a measuring tape or level to be sure.
A piece of pipe insulation wrapped around a screwdriver handle will give you a better grip when you need more torque, or when the handle is just plain slippery.