Copy animation from one blend file to another blend file, which has the same mesh.

Hi,
I have a human model with lip-sync animation. I have another duplicate model of the same. I have added some more lip-sync animation in the duplicate model. I want to copy those updated animation frames into the original model. Somewhere i saw, i need to use Shift + F1 to do this etc. But, i want step by step details, how to do this? How to open two blend files into one and do copy etc.

Can someone please guide me?

Getsy.

Appending tutorial http://cgcookie.com/blender/2010/07/12/tip-appending-and-linking/

For animations, try appending the action. Then in the action editor select this appended action.