Even if you have never had a problem with your MacBook, as the years go by, unused files can begin to clutter the drive. Not only do a lot of files make it harder to find what you need, a full drive also slows down your computer. Mac OS X requires free space to use as virtual memory when it runs large apps or when you do a lot of multitasking. You should keep at least 15 percent of your primary drive free for OS X to use as virtual memory.
Deleting Cumbersome Files
Clean out files and apps that you no longer use to make some room on your Mac's hard drive or flash drive. Search for all the large files on the drive by clicking the "Search" field at the top of any Finder window and selecting "File Size," "Is Greater Than" and then typing a number, like "100" or "200" MB. You can then sort the results by the last time the files were used by clicking the top of the "Last Opened" column. If you find files you don't need anymore, delete them or offload them to an external drive.
Offload Data to Another Drive
External hard drives and USB flash drives are inexpensive enough that you can probably justify picking up an extra one to archive your old files. Unless you're prepared to lose data if a hard drive crashes, you should always have two copies of your files on different drives. If you already use Time Machine to back up your Mac to an external drive, get a second external drive for your archives. There's no reason to spend extra money for a drive formatted for Macs -- your Mac will format a Windows-ready drive automatically when you plug it in.
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Using a Second Partition
Scrolling through long lists of files in Finder or running a search for a specific file can be time consuming on a crowded drive. To manage your files, consider adding a second partition to your Mac's hard drive or flash drive. You can do this in the Disk Utility, located in the Utilities subfolder in the Applications folder. Select the drive in the left menu and click the "Partition" button. Set the size for the new partition and within seconds you have a second virtual drive. This is a handy option if you travel a lot with your MacBook and don't want to lug around extra drives. However, a partition isn't a substitute for a backup drive. If your drive dies, chances are that both partitions will be lost.
Using Disk Verify and Repair
An often-neglected part of keeping a Mac's drive in good repair is using Disk Utility to verify disk permissions and verify disk integrity. Over time, disk permissions on OS X can become befuddled as one program may change permissions set by another program. Click the "Verify Permissions" button in Disk Utility and then the "Verify Disk" button. If there is a problem with the disk permissions or a problem with the disk itself, Disk Utility will offer to repair them for you.