I know, I know: Who on earth ever has leftover wine? But if you do happen to be one of those people every once in a while, and that leftover wine happens to be red, you should absolutely recork the bottle and put the wine in the fridge.
When trying to preserve a bottle of leftover wine, the most important thing is to protect it from oxygen. Even once you’ve placed the cork back in the bottle, there is no way to ensure air isn’t still seeping in while the bottle sits on the counter. The fridge, on the other hand, is an extremely low-oxygen environment, so storing wine there will ensure it stays fresher for a bit longer — two to seven days on average.
When you’re ready to have another glass, simply pull the bottle out of the fridge and let it sit on the counter for 20 to 30 minutes to warm up a bit, then pour and enjoy.