I want to know how to move the local axis of an object so that I can change how it rotates. ex: moving the axis to one side of a door model, making it easier to animate.
If it helps I am using 2.5.
The point that you are looking for is called the object’s center, and you will find various ways to (re-)set it. Depending on the exact version of Blender you’re using, these features were called, e.g. “Center New” (recalculate the center) and “Center Cursor” (set the center-point to be where the 3D cursor is now).
You are definitely on the right track. If you want to “open a door,” then you want the door to pivot around “wherever the hinges are supposed to be,” and the right way to do that is to put the “center” point there. Then, rotate the object “around its center.”
In 2.5, you need to set the position of your 3D cursor to where you want the new center/axis to be (how to do that was just covered here: http://blenderartists.org/forum/showthread.php?t=204616 ), then select the object in question and press Shift+Ctrl+Alt+C, which will bring up a menu with a few different options – choose “Origin to 3D Cursor” and now your object’s pivot point has changed. (Nice: We’ve used “Center” “Axis” Origin" and “Pivot Point” to say the same thing!)
If you don’t need the pivot to be permanent, but only need it for some modeling adjustments, you can set the cursor where you want it and press the period key, which will set the pivot point to the 3D cursor (this will apply to everything you try to rotate or scale, by the way). Then, when you’ve finished, press the comma key to set your pivot points back at the object origins.
If you’re doing something like an opening door, it might be easier to parent your door to another object, even an invisible one, that can act as a “hinge.” All you have to do is rotate the hinge and the door will follow.