Keep bottles on their sides in wine racks, so that the wine inside keeps the cork wet.  If the cork dries out it will allow air through to the wine which will oxidise and turn to vinegar.  It may also crumble into the wine upon opening. If you don''t have a wine rack use empty cardboard boxes with dividers (some off licences/liquor stores give these away) or small lengths of drain pipes can be stacked on top of one another and used in the same manner.