Per Trixie's request, I will explain briefly how to prepare absinthe in the traditional manner. Be warned: no matter how much you like licorice, nothing will prepare you for your first glass of absinthe. This liquor may be as much as 80% alcohol. Enjoy conservatively.
You will need
Absinthe (available from fine U.S. distributors and from more than one bottler)
A perforated spoon, a dripper, or brouilleur
A drinking glass
A 1 ounce shot glass or a willingness to estimate
A sugar cube
Ice-cold water
Pour 1 oz of absinthe into the drinking glass. Place your absinthe spoon atop the glass and place the sugar cube atop this spoon. Slowly drip 3 to 5 oz cold water over the sugar to dissolve it into the absinthe. (Some purist absintheurs abstain the spoon and sugar.) The water will cause the absinthe to louche, releasing the essential oils therein and becoming opaque - a milky yellowish green.