Tips for making macarons

Following on from the Serious Eats post here are the tips that people have come up with:

1. Sift ingredients, no lumps. I would grind the icing sugar/almonds in an electric mixer and if necessary dry them in the oven beforehand.
2. Use old egg whites, cracked and left out of the fridge for 24-48 hours. They won't go off! This is supposed to be key to making a thick batter and so to getting the 'foot' large. Here's a reference to it at KitchenMusings. They also help develop a thicker, stronger 'shell'. Since moisture in the egg whites has a huge effect on the end product, leaving them out probably reduces the moisture. Apperently microwaving the egg whites for 10 secs has the same effect!
3. Fold in dry ingredients to egg whites in parts to not have a too runny a batter.
4. The beaten mixture should for peaks the dissolve back down, not too thick not too runny.
5. Use a double layer of parchment.
6. Place the tip of the pipe nozzle 1/2 inch above the parchment.
7. Slide the parchment off the tray and give it a quick spray of water and replace the parchment. The steam will help release the macarons.
8. Rest the macarons for a day before eating.