First of all, eliminate the oxygen as much as possible. The best way to do that is to transfer any "leftovers" to a smaller container that doesn’t leave a gap in between the wine and the lid. If this isn’t possible, there are a few quick things you can do to the bottle you have opened.

1.	Use a nitrogen gas that is heavier than oxygen to push the air out the top of the bottle.
2.	Pump the air out of the bottle.
3.	Fill the bottle with "wine beads" to fill the depleted void remaining after the wine has been drank. "Wine beads" will not rust or mildew or influence the flavor at all.
4.	Drink the wine quickly.
5.	Cook with the wine that goes bad. You have many weeks to do this.