One of the things that we've been noticing more of recently is "cam" style quick release skewers in dire need of lubrication. This a real safety issue. Many people know the guiding rule of adjusting the quick release tension: make it tight enough that the effort to close the lever leaves the impression of the lever on the palm of your hand. If the barrel in the center of the lever's cam is rusting, however, the effort you are feeling is as much the corrosion putting up a fight as it is actual tightening of the wheel into the frame or fork. Not good! If you see corrosion, lubricate as you see in this first illustration. Otherwise, lube these pieces once a year anyway for good measure.
The old school quick release, where the lever turns inside of the skewer's cap, also needs lubrication. The best way to service these is to remove the skewer from the bike and feed some lubricant into the seam between the cap and the center. Now swing the lever back and forth a few times until you see a little lube working itself through from the inside to the lever on the outside. Remember that when you put the lever back into the wheel, the springs should be narrow end toward the axle!