The idea behind allowing wine to breathe, or aerate, is to increase your wine's exposure to the surrounding air. Allowing wine to mix and mingle with air will usually warm it up, allowing the aromas to open up, the flavor profile to soften and mellow out, and the overall flavor characteristics to improve.

Which Wines Require Breathing?

Red wines, in general, benefit the most from a little breathing time before serving.
Select whites, on the other hand, will benefit from a little air exposure.
Most wines will improve with just 15 to 20 minutes of airtime in general. If the wine is young and has a lot of tannins, it will need more time to aerate before drinking.
For example, proper aeration and flavor softening will take about an hour for a young, mid-level, or higher Australian Cabernet Sauvignon. Not that you can't drink it right away after it's been uncorked, but to give it its best shot, give it a little more time to breathe. Wines that have been aged for more than eight years are a different story. These wines will benefit the most from decanting, with only a brief window of aeration before the flavor profiles begin to deteriorate. 

How to Let Your Wine Breathe?

Some people mistakenly believe that simply uncorking a bottle of wine and letting it sit for a few minutes is enough to aerate it. This method is ineffective because there is insufficient space (read: surface area) at the top of the bottle to allow sufficient amounts of air to contact the wine.

So, what's a wine enthusiast to do?
You have two options for "breathing": decanter or wine glass. 

• Decanter: Pour your bottle of wine into a decanter, a flower vase, an orange juice pitcher, or any large liquid container with a wide opening at the top. Allowing more air to contact your wine is made possible by increasing the surface area. Keep this in mind as you set up your favorite wine's proper "breathing" techniques.
• The wine glass: Pour your wine into wine glasses and allow it to aerate naturally.
  This is the most low-maintenance method, and it usually works well.
  Just keep the glass away from the commotion in the kitchen while it breathes deeply.
  * Tip: When pouring wine into glasses, pour into the center of the glass with at least 6 to 10 inches of "fall" from bottle to glass to allow for additional aeration during the pour. 

Watching and tasting a wine evolve in the glass over the course of a meal or conversation is a fascinating experience.
Many wines (particularly reds) will find a new cadence in the glass, one that is both approachable and engaged, after some time to settle down and dance with a little oxygen.