How do you say I want beer in French?

The translation of the phrase is contingent on the circumstance. If you want a "duck dish" like Peking Duck at a Chinese Restaurant in Pairs (for example), the way to translate is "Je veux du canard." If you are in a pet store and wish to communicate that you want the duck, the way to translate is "Je veux le canard."

Note: "Je veux" is very rude and strong in French (much ruder than it is in English). A much more acceptable expression is "Je voudrais" which means "I would like".