If the wine has a cork, such as Santa Helena Gran Reserva wines, you should store the wine in a horizontal position, so that the cork does not dry out. If it dries, it becomes narrower, allowing oxygen to enter and the wine to be spoiled.
In order to maintain the wine in optimal condition, try to store it in a place which is not subjected to temperature changes, such as in the kitchen or near a heater. The wine is best kept at a temperature of approximately 15°C.
Also, keep the wine away from aromatic elements. Though it is hard to believe, wine is so sensitive that it can absorb aromas from outside the bottle, and incorporate them into the wine (note that this can happen with wines with cork).