Currently Being ModeratedMay 14, 2013 8:36 PM (in response to ashleyha22)
Quit as many programs as possible, next do not turn off the machine, hook up a external drive and use it to move some large files off the machine (Movies work very well) as to free up space on the boot drive.
Moving requires copying then deleting the originals on the boot drive, reboot to regain the new free space in Activty Monitor in your Utilities folder.
If you have trouble copying or it doesn't work, make sure the file sizes are below 4GB on a external FAT formatted drive (normal for new drives)
If you wish to format a external drive so it can hold larger than 4GB sized files, then if it's only to be used with a Mac, then head to Disk Utility and Partition 1: Option GUID and OS X Extended Journaled as the format. (formatting a drive erases all present data on it)
If you use a external drive with a PC, take the drive (free of wanted data) to a Windows PC and right click on it and format exFAT (Windows XP needs to download exFAT from Microsoft first.) Mac's don't format exFAT correctly, so it can't be used with a PC. But the PC formats exFAT correctly and a Mac can read it (go figure?)
Currently Being ModeratedMay 14, 2013 8:32 PM (in response to ashleyha22)
Use OmniDiskSweeper (free) and get rid of files you don't need.
Currently Being ModeratedMay 14, 2013 10:56 PM (in response to ashleyha22)
Select the icon of your startup volume ("Macintosh HD," unless you renamed it) in the sidebar of a Finder window, and open the Info window. How much space is ? Specify gigabytes (GB) or megabytes (MB).