Lucky you since you have Mac OS X. Windows users are envious at how easy this will be.
When you install Linux—and may I suggest you choose Linux Mint 17 Xfce for its ease of setup and ability to mimic the Mac desktop—you need to setup a USB FlashDrive for the install.
Tools to create such a drive include Penguintosh—and there's a tutorial for using that here—since you must initially create the USB drive image as an EFI compatible hybrid device.
As an alternative for USB flash drive creation, you can do it all in Mint as explained here.
Lifehacker Australia also has a step-by-step tutorial on making your Mac dual-boot.
Then—once installed—the GRUB2 menu will appear and ask which OS you want to boot into.
If you want the default OS to be your Mac OS X, then edit GRUB2 as so:
Make a backup of your current GRUB2 config file like this:
sudo cp -an /etc/default/grub /etc/default/grub.sav
And then edit the GRUB2 config like this; for this example we are using
nano but you can use any text editor you wish:
sudo nano /etc/default/grub
Find the line that contains
GRUB_DEFAULT=0 and set it to
X is the index of grub menu item for Mac OS X.
Since the numbering is based on zero indexing, the first item in the list is
0, the second item is indexed as
1, the third item is indexed as
2 and the fourth item is
3. So to boot to the fourth item in the list, the line should say
Then rebuild the updated grub configuration by running this command:
Reboot your machine & you should be all set.
As an alternative, you can just boot directly from the USB flash drive if you wish. But the instructions above allow you to create a nice dual boot setup on one drive.