How to copy files on Mac OS X using drag and drop

"When working with Mac OS X, to copy a file (or multiple files) from one Mac Finder folder to another, just hold down the [Option] key when dragging your files from one folder to another. This magic keystroke tells the Mac Finder that you want to perform a copy operation, and not a move."

http://devdaily.com/mac-os-x/mac-copy-files-mac-finder-copy-files

http://devdaily.com/blog/post/mac-os-x/copy-files-drag-and-drop-mac-os-x