Change the default center point of a symbol to allow for easier character animation
When animating body parts, it's important to make sure that the symbols are rotating from spots representing joints on a real body. Doing this will make animating your character much easier as the symbols will rotate around logical pivot points. There is a very easy way in Flash to alter the pivot point on a symbol.

When you click on a symbol, you will see a light blue border around it and in the center of the symbol will be a round circle with cross hairs in the middle of it. This circle represents the pivot point of the object. When you rotate the object, it will use this point to rotate around. The object will rotate differently according to the location of this circle.

For example, if you have an arm symbol that you want to animate, the logical pivot point would be at the end of the object, near the shoulder. To change the pivot point, you first click on the symbol to make it active. Then you use the "Free Transform Tool" to allow you to change the pivot point. There a number of ways to get to this mode. The quickest way is to use the hotkey: "Q", or you can click on the transform tool in the tools window which looks like a square with dots around the edge of it with one in the center.

IMPORTANT NOTE: Set the pivot point BEFORE you begin setting keyframes
It's important to note that if you want to change the pivot point somewhere other than the default which is in the center of the object, you need to set it before you start setting keyframes on it. Doing this will make sure that the pivot points are all the same on all of the keyframes. If you decide to change the pivot point on one keyed symbol, it will not change the pivot point for all of the other keyframes. When you motion tween the symbols you can get some undesirable and unpredictable results with the motion of the symbols.