Basically, as per the recipe that I received from a good friend, who got it from his father who lives in Italy, it goes like this:
1.75 liter bottle of Everclear (or whatever version of grain alcohol you can get your hands on)
zest 15 lemons
put the zest in the everclear, and let that sit for 2+ weeks ion a cool dark spot.
Filter the zest & everclear, and you'll have a nice yellow color on the everclear. Set that aside.
Get 6 cups of sugar and 6 cups of water, and heat the water (do not boil), pouring in the sugar until it is all dissolved. Let this cool to room temp.
Add the sugar water mix (called simply syrup or simple sugar) to the filtered everclear, and then add another 1.75 liter bottle of everclear.
Let this combination sit in a container for another 2+ weeks, once again in a cool, dark spot.
So basically you have two 1.75 liter bottles of everclear, the zest of 15 lemons, and 9 cups of simply syrup, and a month of them mingling... This is decantered into a small container, and placed in the freezer (don't worry, it won't freeze). It is served straight from the freezer into a shot glass, where--in Italy--it is sipped after dinner.
I've also done vodka batches which are easier to drink, but vodka doesn't pull the essence out of fruits as does everclear. I have a batch that I made with orange that just finished in my closet. I need to put some more in the freezer for tonight / tomorrow.