It's critical that the fence be parallel to the saw blade. If it's not, the blade will bind on the wood and cause a burned edge on your board, or worse, a dangerous kickback. If you have a saw with a top-quality fence that locks down squarely, then you should only need to check and adjust the fence the first time you use it. Read your owner's manual for instructions on adjusting your fence. Fences on less expensive saws can be inconsistent, and you'll need to check every time you reposition the fence.
Here's how: Measure the distance between a saw tooth and the fence at the front and back of the blade. Raise the blade fully for the most accurate check. For an accurate reading, make sure to choose two teeth that lean toward the fence. If the measurements are different, either adjust the fence or nudge it into position until the measurements are equal before locking it down.
