LOCAL PRINTING: When it comes to short run printing, the local option is my favorite option. Local print shops may not be able to match the price of many online vendors, but you get to have more of a hand in the process, and therefore a little more control over the end result. Some will even let you bring in your own paper, and most will let you use their paper cutters for free (sometimes even if you haven't printed anything through them). Unfortunately, not all local shops are created equal—some FedEx Office shops are great, others not so much. You'll need to do your due diligence to find a good match. InkerLinker is also a good place to find amazing, non_FedEx print shops near you.
POSTAGE and Quantities: The number one tip you need when it comes to sending out your invites, is that your guest list number does not equal the number of invites your sending. Do the math on how many couples you have ahead of time, and you won't make the common mistake of ordering about double the invites you need.