If you are using iCloud, and have contacts turned on in iCloud, then you don't have to decide how to share contacts between your devices and other computers. iCloud handles that automatically.
If you are not using iCloud yet, then it's a little more challenging, in that you need to use iTunes to share contacts, and sharing from your iPod to you Mac is not the normal direction for that sharing. You CAN use a utility such as iPod.itunes, which makes that process simple. http://www.macupdate.com/app/mac/7546/ipod.itunes