Depending on which model iPod you have, the steps for resetting it may differ. For the iPod Nano, hold down both the Sleep/Wake button and Volume Down button at the same time while counting at least eight seconds, or until the Apple logo shows up. If it doesn't work, repeat. If you're still having problems, connect the iPod to your computer (when the computer is turned on, not when it's in sleep mode) or plug it into the power adaptor, which you'll then plug into an outlet. Try to reset the iPod when it's connected to a power source.
If you have an iPod with a click wheel, put it on a flat surface, slide the switch to Hold and turn it off, and then hold down the Center (Select) and Menu buttons at the same time for six to eight seconds until the Apple logo appears. Repeat if it doesn't work. If it still doesn't work, connect to power source as above. If you're the proud owner of an iPod scroll wheel, touch wheel, or dock connector, slide the switch to hold, and turn off, then hold down the Menu and Play/Pause buttons at the same time for six to eight seconds until the Apple logo appears. Repeat if it doesn't work. If it still doesn't work, connect to power source as in the first paragraph.
If you want to reset an iPod Shuffle, disconnect it first from the computer (if it's connected), and put the switch in the OFF position. Wait from five to 10 seconds, then move the switch to the Shuffle or Play in Order position. If you have an iPod Shuffle second or fourth generation, move the power switch to On. When the iPod is off, you won't see the green line near the switch; when it's on, you will.