Getting a properly chilled cocktail simply means making the best use of ice in chilling it down. There are however many methods of doing this which might at first "sound" like a good idea, but in fact aren't.
Cocktails should be cold, Icy cold. Ideally, a properly prepared cocktail should be as close to 32 degrees (the freezing point of water) as possible. You can do this by either shaking the drink with ice, or stirring it. Both do the job equally well. When two components of differing temperature are combined, thermal transfer takes place in order to bring the temperature of both ingredients into a state of equilibrium. This means that the cocktail gets colder, and the exterior surfaces of the ice gets warmer. As the ice warms up, it releases water into the drink.
In order to speed this process up, you might find yourself tempted to store the ingredients for your cocktails in the freezer. Doing so would start the cocktail off at a temperature that is already at the freezing point, or close to it. Not only would this speed up the chilling process of making the cocktail, but since there is less thermal transfer going on, this also means that their would be less melting of the ice being used, which would result in less water released into the drink.
Many might say that this sounds like a win-win situation. Not only is the drink prepared quicker, but it is also less diluted. Yes, this might be tempting, but it would also be very wrong.
The problem with storing your liquor in the fridge/freezer comes about because of the mistaken assumption that water is "bad" in a cocktail. Nothing could be further from the truth. Water is in fact a very important ingredient in a properly made cocktail. It softens the drink down, removing the rough edge that the alcohol naturally carries. And if you put 2 ounces of booze into a cocktail shaker, then regardless of how much ice gets melted, that very same 2 ounces of booze still comes out. You aren't diminishing the alcohol at all with the added water, just slightly increasing the overall size of the drink.
The Art of the Cocktail is all about balance. Take the Martini for instance; a properly made Martini is one in which all of the ingredients blend together in such a way that it provides a wonderful balance in its entirety. Gin has the fiery texture of the alcohol and the sharp botanical notes of the juniper and other herbs and spices. Dry vermouth has the softer, almost buttery texture of the wine which is its base, as well as the more rounder flavors of the herbs used in its recipe. The orange bitters has a spicy flavor with a slight hint of sweetness which provides a nice bridge between the gin and vermouth, and lastly the water provides a non-descript toning down of the flavors in order to make the cocktail gentle and sophisticated.
In this crazy “Bigger, Better, Faster, More” world we live in, it is easy to get confused with what really is important when considering quality products. Just as some might think that the spicier an Indian Curry is the better it is, some might also think that the more of an alcohol burn a cocktail has, the better it is. I suppose if all you are interested in is getting drunk, then that makes some sense, but the cocktail is far more then that, and it should be presented with the same subtle sophistication and balance of flavors as a finely crafted Indian meal should have.
So do yourself a favor, and keep your booze out of the freezer.