- Smell your wine
Deciphering between the way wine should smell and the way wine should not smell is pretty easy. When a wine has gone bad it usually has a vinegar smell and a corked wine usually has a musty smell. If the wine smells normal or even fruity than it is probably still good, if it smells different then you might want to go ahead and dump it down the drain.
- Check your balance
Checking the balance of your wine is very important. Factors including the acidity, tannin, and alcohol all need to be balanced properly so that none of them stand out more than the other flavors do.
- The finish
Testing the way your wine finishes is a great way to tell if wine is still drinkable. Depending on how long the flavor lasts in your mouth, the better the wine is. So go ahead, take a big ol’ swig of your wine and see how long the flavor stays on your palette.
http://www.quickanddirtytips.com/house-home/entertaining/wine/4-ways-to-know-if-your-wine-is-good