By far the biggest surprise for me was Stella's advice to let the baked and sandwiched macarons chill out in the fridge for about 24 hours before eating them. She says this ripening period helps improve their texture and flavor. I had no idea!
Another commandment I will be taking to heart is rapping the pan firmly before baking. This encourages any bubbles in the batter to find their home elsewhere; if left behind, these bubbles will create unseemly cracks in the surface of your macarons. I've done this step before, but after reading Stella's description, I think I haven't been rapping that tray nearly hard enough.
Whether you're a veteran macaron-er or plotting your first attempt, this post is a must read:
• The Ten Commandments...Of Macarons from BraveTart