also, before you take guages out, turn key to on position, so that the guages "zero" themsleves out. like the oil temp will fall to zero, and other guages will settle.
If all else fails, especially for gas guage, drive around till you gas light comes on then, put the needle on.
Be careful whe doing this and look under the needle first before you do it. On some of the other needles you'll see a clear plastic finger pointing at the gauge mechanics to pickup light to brigthen the needle at night with the lights on.