I have a recipe for macarons that works well; it says to use 2 trays while baking to get the raised lip.   I find if I crust the macarons overnight, that the lip comes up because the goo inside explodes like a volcano ripping apart the outer layer crust. My question is though: what are the optimal conditions - should the oven be hotter or warmer? how long is long enough for crusting  Finally, how do people make them in such nice neat shapes? Mine always come out looking misshapen. 
I was lucky enough to get a macaron session from a Michelin-starred pastry chef before Christmas and he gave me some invaluable tips.   Use an Italian meringue recipe. In other words, pour warm sugar syrup on to the egg whites instead of sugar from the cupboard. The eggs will already have been 'cooked' into structure and will not require any crusting. They will retain the same shape that you pipe them out at. You can bake them straight away, or in a couple of hours - they won't be any different. When piping, use a moderate pressure. Don't wring the bag out. Keep the nozzle approx 2cm over the tray and maintain that height while you pipe - let the weight of the batter spread the macaron out evenly. When there is enough mixture in place (about 4cm across?) stop squeezing and flick the nozzle away in a controlled circular motion to avoid creating a 'nipple'.   I wrote about this including his recipe on my blog here.  PS. I just remembered that adding further weight to the Italian meringue technique a very prominent French chef in the UK, Raymond Blanc, said that he always uses this method. On his TV programme this week he said it delivers far more consistent results. 