This is for my own reference, since I keep referring to the Ubuntu guide.

1. Optional: convert an ISO to an IMG

   hdiutil convert image.iso -format UDRW -o image.img

2. Find the USB stick drive name

   diskutil list

3. Unmount it:

   diskutil unmountDisk /dev/diskN

4. Use dd to actually write the image:

   sudo dd if=image.img of=/dev/diskN bs=1m

5. Eject the drive:

   diskutil eject /dev/diskN