You do need a permit. Go to town hall and you get it in the same wing of the building where pool passes and dog/cat licenses are. I don't recall the cost but it wasn't outrageous.
After that consider getting an ad here on MOL. I did and more than a few people who showed up mentioned seeing it
Promote your business here - Businesses get highlighted throughout the site and you can add a deal.
Do I need to get a permit or anything to have a garage sale? Or can I just do it?
Thanks