I harvested my onions this week!
As the tops started to droop, I pushed over the rest of the tops and let them sit in the ground for 3 days in the hot sun. Then I moved them to an old screen door I laid between two saw horses and set them to cure. Generally curing takes a week or more. They must be out until all the green in the stems is gone, the roots are dry and brittle, and the onion skin is good and papery.
At that point you can store them in a cool place as a braid or in a mesh bag or basket. I choose to keep them next to my panty shelf in the garage in a mesh basket. I do not store onions with potatoes or squash due to the fact that they give off a gas that causes them to rot faster. I just consider onions not to play well with others. ;)
They are fine to use while waiting for them to cure, but until they are cured, they do not store well at all. In my case, I will go out and get one off the curing screen when I need one.
I turn them every few days to make sure all sides dry evenly and when the tops are brown and dry I will braid some to give as gifts to neighbors and friends.