Do you know why your waiter pours just a little bit of wine for you to try before pouring the rest of the bottle? And what are you supposed to do with the cork that is set on the table? The sample of wine is make sure that there are no faults with the wine; not to see if you actually like it. As for the cork, you can look at it but please don't smell it! If there are any markings, such as a date, stamped on it, make sure that they match the wine you ordered. If they don't your wine may have been tampered with. What happens if something is wrong with the wine or the cork? Simply notify your server and they should immediately correct the problem with a new bottle.
While not at a restaurant, I encountered a faulty bottle at home this week. One of the two glasses in the photo is flawed while the other is not. A few months ago, I saw a older Chardonnay from a Colorado producer that I enjoy on a clearance rack at my local wine shop. I knew that this particular producer doesn't add sulfites (used as a preservative in wine) and the storage conditions at the store weren't ideal but I decided the rewards of an aged Chardonnay outweighed the risks for only $12. I finally decided to open the bottle and wasn't all that surprised when the wine poured a deep golden brown color and smelled oxidized. Sure enough, the wine tasted very sherry-like (sherries are the most oxidized wines in the world but are made that way intentionally). The wine was undrinkable so I had to open a back up. Disappointed with this outcome, I didn't feel like opening another full bottle, so I decided on a 187 mL bottle of cheap California Sauvignon Blanc that I keep on hand for cooking. While the wine wasn't very good, there were no faults. So if this situation were to arise in a restaurant, don't hesitate to reject a faulty bottle of wine but if just don't like a wine it is what you ordered. If you have questions about a wine, any well-trained server or sommelier will be able to determine any faults for you!