The ritual of decanting wine is nearly as old as the glass bottle. There is a common misconception that a wine should only be decanted if there is sediment that the wine needs to be decanted from. Although this is a very important reason to decant a wine, it is far from the only good reason. Equally important is the fact that decanting a well-made wine allows the wine to react with air, forcing it to "breathe" and give up its full potential flavor. Indeed, it is a shame to buy a good bottle of wine and not decant it, as much of the wine's potential will be left in the bottle.
It should be noted, however, that not every wine needs to be decanted. In fact, many if not most "modern" wines which are made to be drunk soon and quickly do not benefit, and may even fall apart more quickly if decanted. Decanting is a good test to see if a wine is of a quality such that it will "lay down" (age well). If one was to pour a taste from the bottle upon first opening, then decant the wine, then taste the wine once decanted and there was no measurable improvement in the wine quality, one could safely assume the wine will not age. However, a good, cellar-worthy wine will almost always improve upon decanting. Incidentally, this rule applies to white wines as well as reds, and everything in-between.
The length of time one should decant a wine before enjoying it varies greatly depending on the quality of the wine and its relative youth. In general, the younger or higher-quality wine will need longer to "open up" than the older or less high-quality wine. This is not a set-in-stone rule, and one should experiment with every good wine to find its optimum decanting time (a good reason to buy more than one bottle). At Blackwood Canyon, we recommend decanting the bigger Chardonnays at least a day, whereas the reds need at least three days and up to two weeks to open up fully, depending on the wine.
The process of decanting is a simple one, but takes some practice. There are four necessary elements - a cellar-worthy wine, a good decanter large enough to hold a complete bottle of wine with some room to spare for the air contact, a cork-puller that does not agitate the bottle upon opening, and a good light source. Historically, the last requirement was provided by a candle lit in the cellar to backlight the bottle, and this is a romantic practice, but for most people a simple lamp or ceiling fixture will work.
First of all, the bottle of wine should be "stood up" a couple of days prior to decanting to allow the sediment to settle to the bottom. Secondly, the bottle of wine should be (gently) opened and held up to the light source so that it is possible to see "through" the bottle. Third, slowly tilt the bottle and the decanter together at roughly 45 degree angles until the wine begins to pour into the decanter. The wine should not 'splash' into the decanter, it should run down the side. It is very important that once the process of decanting has begun, it is not interrupted, otherwise the wine will back-flow into the bottle and stir up the sediment. Continue gently pouring the wine into the decanter until the sediment from the bottom of the bottle reaches the neck (you should see this clearly with the background light source), and then stop pouring. There will be some wine and sediment still left in the bottle - this is normal - we recommend you use this do deglaze your pan when you are making the sauce to go with the meal that you are preparing to have with this decanted wine!