Q: HI, I just got some killer hash from a friend....how is that made???
-YFH
A: The latest and greatest way involves ice, water and some specialized bags called Bubble Bags and produce a high quality product that "Bubbles" when smoked. Other methods include Dry Screening, Solvent Extraction, ect.. For a basic overview and some historical data on Hash, check out the wikipedia page on hash.
Now for the good stuff. How to make wicked hash, by Liza Scammel and Bianca Sind (23 May, 2002). This is a great article that I came across and should answer most your questions about the whole hash process, including how-to's for several methods of producing hash.