The consensus among wine geeks is that the best solution is to keep a few 1/2 bottles (375ml) lying around, pour the remaining wine from the open bottle into the smaller bottles, fill to the brim, and recork. Then, put the 1/2 bottle in the cellar or refrigerator. This approach can get you up to 5 days of life for many wines before they go downhill.
One of the better ideas I’ve seen.
What are some other tactics you’ve used?