Adjusting the pilot light flame on a gas furnace is the best place to start, if it appears that your furnace is not getting as hot as it used to or if it seems like the flame goes out a lot. This is a very simple process and will only take a couple minutes. The most important things to remember are the various safety precautions you must take when working around gas and fire.
Locate the access plate on the front of your furnace, and unscrew the screws that are connecting the access plate to your furnace. This will allow you to actually see the flame.
Observe the flame. If the flame appears to be too small or sputters on and off, then the simple solution would be to adjust the size of the flame using a screw that you will see on the pilot light.
Turn that screw counter-clockwise, and the flame should grow. Do this if you believe your flame is too low.
Rotate the screw on the pilot light clockwise, and the size of the flame will decrease. Your flame should be a consistent height, and it should not appear to be flickering.
Return the access place to the front of your gas furnace. You will simply do this by re-screwing it back into place until it is tightly secured.