And now I present you with:
Error404's Guide to Drinking Maté
Maté is generally sold in 1Kg cubes at health food stores and Mennonite grocery stores. If you pick it up at the Mennonite grocery stores, it'll be a lot cheaper than buying it at the health food store (Mennonites generally drink it out of tradition instead of out of health concerns).
Now, you'll need one or two other things to drink it properly. One of these is a Bumbillia, which is a metal straw with a screen on the end that makes it look something like a spoon with holes. It's rather imperative that you pick one up, as drinking mate without one will be more like eating. The other thing is not particularly important, but it's neat to have. It's called a Guampa, and it's a cup made of usually bullhorn, or if you're not a Paraguayan beef rancher, a gourd. If you don't have a guampa or don't want to buy one, a small glass will work fine.
Now, put a 3 or 4 tablespoons of maté in your guampa/cup. Add an inch and a half or so of hot water on top of it. Mix it up with your bumbillia, just to get all the maté grounds wet. Push the bumbillia to the bottom of the cup, so that the water/maté covers the screen. Now drink it from the straw. When you can't get any more water out of it, pour about the same amount of hot water over top, and drink some more. Continue this until you get bored, or it gets to be too weak.
If you want to get REALLY traditional with it, you'll drink it with friends, passed around in a circle (kind of like a joint).
Maté: Mennonite ganja.