How to tell if a noun is feminine or masculine?
Apparently Koch (cook) is masculine and Suppe (soup) is feminine.
This is aggravating.
Indeed it is, but as far as I know you just have to remember the articles. Sometimes suffixes may be helpful (nouns ending by "-ung" or "-in" are all feminine I guess) but generally you just have to know what gender the word is. This http://german.about.com/library/weekly/aa042098.htm article is quiet helpful in this matter.