First choose a decanter. Decanters are usually made of glass, and should be large enough to hold an entire bottle of wine and leave some breathing space. Before decanting, allow the bottle to stand upright for several hours, giving the solids a chance to settle. When pouring, place a light source behind the bottle so you can see the sediment, and pour the wine into the decanter slowly, stopping just before the sediment reaches the neck of the bottle. You may have to leave an inch or so of wine behind. If the sediment refuses to settle, try pouring the wine through cheesecloth, gauze or even a coffee filter.
Some wines without sediment can benefit from decanting, particularly if they are young or full-bodied and complex red wines. Contact with oxygen can soften harsh tannins and let fruit flavors come forward. When you are decanting for this purpose, let the wine splash a bit while pouring into the vessel, and give it a few good swirls before letting the decanted wine sit for 30 to 60 minutes.
Older wines should be served shortly after decanting, without too much splashing or swirling, as too much aeration will begin to erode the delicate aromas they’ve acquired with age.