Decanting is a complicated process, but done correctly it provides immense rewards in tasting young red wines. Please keep in mind that this process requires 2 days of advance planning.
I learned this decanting technique 30 years ago from my dear friend Miklos Dora who was the US representative for Mouton Rothschild for 45 years. He has retired, living in Santa Barbara and at 100 years young he still enjoys good wine, especially the Kapcsandy wines.
For red wines that are 15 years or younger (1998 - 2013), most of the time we do not decant and will not use any aerators at all. We stand up the bottle overnight in our cellar or cold dark place (60F or less)…this will allow all of the sediments to come out of solution and settle to the bottom.
Pull the cork from bottle while standing upright. Gently pour a small sample into a glass, smell and taste for any faults or problems (spoilage microbes) with the wine such as TCA (corking), Brettanomyces (barnyard), Acetobacter (vinegar and ethyl acetate), Lactobacillus (mousey and sulfides), Pediococcus (ropy, histamine and tyramine), rustic (over oxidized) etc. If you detect any of these, don't go through the rest of the ritual. The aromas will not flash off and the wine will be lousy.
If the wine is good, allow the bottle to stand upright with the cork pulled for 8-12 hours in a cold dark place (65F or less). We taste a small sample in a good Bordeaux glass, like the Riedel Vinum series. Most of the time the wine is nicely open and no decanting is needed. However if we feel that the wine will further benefit from decanting, we pour the wine gently into a decanter 1-1/2 hours before serving it in the glass.
This works for me every time.