You may already be aware that the Finder allows you to copy and paste files and folders to move them around on your Mac: Select a file, choose Edit -> Copy, navigate elsewhere, and then choose Paste Item. Now you’ve copied the file, and it exists in two places.

If you hold down the Option key, that Paste Item command changes to Move Item Here instead. Now instead of duplicating the file in question, you’ve changed its location on your Mac. Great!

But here’s the hint: Hold down Shift and Option together, and the command becomes Paste Item Exactly. (You can use the keyboard shortcut Shift-Option-Command-V if you’re dextrous.) When you select that option, the Finder prompts you for an administrator password. This option ensures that the file’s original ownership and permission settings (that you’d set via the Get Info panel, or via the chmod and chown commands, for example) are maintained exactly.

Source: Mac OSX Hints