I’m a big fan of the hinged bubble stoppers that you can find for less than $10. If you put a regular cork back in an open bottle of bubbly, the pressure from the carbonation inside might cause it to pop out. The best thing you can do is keep the bubbly cold in your refrigerator—carbon dioxide is more soluble in cold liquids than in warm, so keeping the leftover bubbles well chilled will help keep your wine fresher and more bubbly than if you left it out on the counter.
Along those lines is the theory of sticking a metal spoon in an open bottle of Champagne—the metal will act as a thermal conductor and help keep the inside of the bottle extra cold. If you don’t have a good stopper around, a metal spoon can work in a pinch. But no matter what method you use, your bubbly will become flat once it’s open for a day or two.
Fonte: http://www.winespectator.com/ (Dr. Vinny)