Hi N C Gupta,
Champagne Lanson Black Label Brut : Don't wait too much. A good champagne but best consumed young, fresh and very chilled !
Kriter extra leger Brut : Same as above...have even before the Lanson.
Martell V.S.O.P. Medaillon Old Wine Cognac : Cognac once opened can keep easily. Just preserve the cork. It is a spirit (like whiskey). VSOPs are best enjoyed in an old fashioned glass (the snifter is passé) with ice. Put the ice first (two-three cubes) and then pour the cognac on top. You can also have with soda, tonic or water as you like.
Seitzer Ausstich 1996 11.5% vol. Trocken : A fairly medium-dry wine, chill it well and have it now!!!...its beyond its prime.
Velho Barreiro ( Hofer) Aguardente de cana Adocada : Aguardente is like tequila as in same plant but outside the designated region. Depending on how it was aged (does it look golden, well then it was aged) one has it in various ways. If its colorless and young have it chilled and in shot glasses. You can also blend into cocktails. If aged, have it like cognac with ice in an old fashioned.