Both dry and dessert Semillon should be served chilled.
Most dry Semillon is ready to drink when released, although the better French examples can age up to a decade. Dessert wines can age incredibly well, easily a decade or more, although most can be enjoyed when released, which is typically three to four years from vintage date.
Store bottles in a cool, dark place. While it is now common for wine makers to use plastic corks or screw-top closures which may be stored vertically or horizontally, those with the traditional corks should be laid on their sides to keep them moist.