Depends how you wish to do it. More than one way.

Personally I do not share my downloads. I have my own set of shares. So in that way I am not sharing a file twice.

Go to LW's preferences -> My Files, uncheck option "Add files I download from P2P Users to my Public Shared List."

Any files or folders you wish to share you can simply drag & drop them onto the Public Shared icon on left side of LW. They will automatically be shared then. You could potentially do that for the entire iTunes Music Library if you wished. Example image: Drag files/folders to Share sample image or see more methods here http://www.gnutellaforums.com/gettin...w-5-2-8-a.html

Make sure you are sharing files.