Also for older bottles, check the wine cork for leakage after you have removed the foil covering and look at the level of wine in the neck of the bottle to make sure that not too much evaporation of wine has taken place with bottle aging.
Both the guest and the wine server should observe the level of the wine in the unopened bottle. A low level indicates evaporation (which may be normal in an old bottle) or leakage which would be abnormal. If the guest does not notice this, you should point it out to involve them in the circumstances which could result in a bad-tasting wine.
Either observation increases the probability that the wine is oxidized. Any “crud” around the neck of the bottle under the foil cap definitely indicates wine leakage either due to a damaged cork or excessive heat exposure.
A ”cruddy” cork may indicate a “cruddy” wine.