Step 0 - Download Raspbian OS

The first thing we need to do is download Raspbian OS.

Once the disk image has been loaded, we'll want to open up Applications/Utilities/Terminal

Step 1

Before adding your SD card, first take notice of which disk volumes are mounted.

df -h

Now add your SD card and see if you can identify the card

df -h

In my case, the SD card is /dev/disk2s1

Step 2

The next step is to unmount the SD Card.

sudo diskutil unmount /dev/disk2s1

Next step is to figure out the raw disk name of the card by adding r and removing s1.

/dev/rdisk2

Step 3

Now use the Unix utility dd to copy the image bit-by-bit to the SD card

# Run as root and copy the input file to the output file
sudo dd bs=1m if=~/path/to/raspbian.img of=/dev/rdisk2

The final step is to just wait.