OSX: Move Files Instead of Copying
You do not have to copy and then delete when moving files on your apple box. Here is how to do it all with one command. This tutorial describes how to drag and drop to move a file from one location to another.
When copying files from one location to another, I have always found it an annoying process to drag the files to one location and then go back and delete them from the original location.
The default drag and drop process in OS X is to COPY files.
We want to be able to MOVE files.
To MOVE a file is to actually copy files to a new location and to delete them from the original location.
OS X will move the file if you hold the CMD key while you drag and drop.
One caveat:
Something that confuses people is what happens if duplicate files are found during the move drag and drop. If you release the CMD key to answer the dialog box that appears, the file will be copied but not moved. If you continue to hold the CMD key as you click the Replace button, the move action will be completed.
source http://www.tech-recipes.com/rx/2581/os_x_move_files_instead_copying/
