Port wine should be stored in the same way as any other fine wine, and whilst a proper wine cellar at home would be the perfect solution, few of us have this facility.
However, you can store Port perfectly well at home in a cupboard. The most important consideration when storing Port is to keep it away from direct light in a place which doesn't have large fluctuations of temperature and ideally where the temperature does not exceed 15ºC (60ºF).
Storing Port at temperatures above this level may be detrimental, resulting in the Port ageing too quickly.
As with all fine wine, to keep it in optimum condition all Vintage Port should be stored lying down in order to keep the cork moist. Vintage Port bottles have white splash of paint on one side which should be always kept uppermost when laying down the bottle.
In this way, the natural sediment in the Port is always maintained in the same position. For this reason, before opening a bottle of Vintage Port, always stand a bottle of Vintage Port for a few hours to facilitate easier decanting.
It's also important to keep your Port away from vibrations which would have the effect of stirring up the sediment in the bottle. The cupboard next to a washing machine, for example, would therefore not be a good idea!
If you have the space, a refrigerated wine cabinet would be the perfect way to store your Port wine at a constant and optimal temperature. Should you be lucky enough to have large quantities of Vintage Port to store, most professional wine merchants offer a cellaring service which will not only ensure it is stored in perfect condition, but will also insure the investment value of your Port over the coming years.