1. Give it a bash
For a long time I made my macarons as the recipes stated, even letting them rest, yet they always came out cracked on top and I couldn't work out why. Then one day, I was looking up tips for macarons and it said to hit the baking tray to remove excess air bubbles. So, I made another batch and dutifully did as it said and, although still not perfect, the macarons didn't crack on the top - just by hitting the tray.
The consistency of the macaron batter should be just right: not too stiff and not too loose. I've heard it described as 'magma', you'll know it's there when if the batter is dropped from a spatula it can sink back into the mixture in 10 seconds. You should err on the side of too stiff: too thin and it will just spread out like a pancake.
When piping the macarons, make sure they are far enough apart that they won't spread into each other, 1-2 cm is about right: there's is nothing more annoying than an otherwise perfectly good batch of macarons which has merged into one.