Organize your Mac's data by moving it, not copying it
When you’re ready to organize the data on your Mac, create folders and subfolders that represent the data you want to keep. After creating the folders to store your data, move the data into them. Notice I’ve used the word “move.” If you copy the information, it will be in two places. Having data in two places complicates things and uses up unnecessary space on your hard drive. There’s no point in copying your pictures into subfolders if you’re going to leave a copy somewhere else. That’s not organizing, that’s creating more clutter!
Sometimes you need to be able to access data from multiple places though. If you want to have multiple access points to your data, you should consider using aliases. Creating an alias for your data isn’t considered moving it. (Recall that an alias is simply a shortcut to the data.)
For more information read Managing Aliases on Your Mac.
To move data from one folder to another on the same disk–for instance, from the Pictures folder to a subfolder you’ve created inside of it–follow these steps:
Open the Finder, your Home folder, and then the folder that contains the files to move.
Select the files to move by clicking or dragging over the pictures with the mouse.
Drag the items to the new folder. To place the items in a subfolder inside the folder, hover over it for a second and wait for the subfolders to appear. Drop the file while hovering over the appropriate folder.
Tip: To copy the file instead of moving it, hold down the Option key while dragging.
This procedure, to move data, is one you’ll use often. Drag and drop from the desktop to folders you’ve created to keep data organized, or drag and drop between folders to get organized. You can also use the Edit menu to copy and paste a file. Copying and pasting a file isn’t moving it, though, so be careful!
There’s an exception to how this dragging and dropping works though. If you try to use the this procedure to move a file from one disk or partition to another disk or partition (for instance, from your computer to iDisk, part of a .Mac subscription) or to a backup device such as an external drive, the file will not be moved—it will just be copied. This is because Apple figures if you’re dragging from one disk to another, you’re probably backing up the data, not moving it. Make sure to keep all of this in mind while dragging and dropping data.
Caution! If you try to copy the contents of a CD to your hard drive by dragging, you’ll only get an alias of the drive and not the actual contents of the CD. To get around this, hold down the Option key as you drag.