If you plan to pour from the same bottle the very next day, you can simply re-seal it and leave it on your kitchen counter – under one condition: the room temperature of your kitchen does not get above  normal room temperature (72 degrees) in the course of the next 24  hours. (If it does, put the bottle in the refrigerator.) Find a cool  spot for the bottle and feel confident the next night that the wine will taste as good as it did the first night. And don’t be surprised if on the second pouring the wine’s flavors seem a bit more interesting than it did the first night. Some wines will noticeably improve with just enough exposure to air, like the amount it would  see sitting inside a half-full bottle overnight. If your wine happens  to be one of them – and there’s no way to predict which ones will  improve significantly – the second night’s taste will be a real treat.
But let’s say you aren’t sure about when you will re-pour from this  bottle. Maybe the next night, but most likely it won’t be for a few days. Then you should refrigerate the bottle after re-closing it,  whether it is red or white. Refrigeration will slow the aging process down enough for you to enjoy the bottle again in several days. It should stay as fresh as it was the first night for 2-3 days. More than this and it will begin a gradual decline through the process of  oxidation. Remember, the closure you use to re-seal the bottle is not perfect. Some microscopic amounts of air will creep inside the bottle over time.
Now, for the wine-saving gadgets. There are several tools on the market designed to keep unfinished wine fresh overnight. One pumps  the air from the bottle through a slit on the top of a custom rubber closure. This product works just fine, and will extend the life of  the wine longer than simply re-sealing the bottle with the cork. So  you can add at least an extra day, maybe two, to the shelf life of the unfinished bottle, again, assuming the room temperature does not exceed 72 degrees.
Another tool is an aluminum canister filled with a harmless and odorless gas. A tubular spout can be placed through the neck of the  bottle as you shoot a few bursts of gas into the bottle. The gas  pushes out the oxygen and replaces it, acting as a preservative. You  then immediately seal the bottle with a suitable closure before letting the gas escape. I have found this process to work very well and use it regularly. As an added safety margin, I will refrigerate  the wine also. Bottles will remain fresh for 4-5 days, sometimes more.

Len Napolitano lives in Central Coast wine country and is certified in wine by the Society of Wine Educators, Wine & Spirits Education Trust, and Chicago Wine School and continually gains knowledge from his frequent contact with California winemakers. More information is on his website, www.wineology.co . Send your questions about wine to: wineologist@earthlink.net or by mail to Len Napolitano in care of Wine Country This Week magazine. Wineology is a registered trademark of Len Napolitano.com