Try not to expose the wine to strong light, especially sunlight.
Do not expose wine to exessively low or high temperatures, ideally they should be stored at around 13 degrees C. Store in an area where the temperature does not fluctuate.
Store the bottles on their sides in a humid environment to prevent the cork from drying out and crumbling.
With older and more substantial red wines then it is often better to decant them a couple of hours before you intend to drink them, this will let the air get to the wine and help to bring out more of the flavours.