Here is what you need:
Mission falls 1824 wool, or another yarn that is worsted weight (18 stitches per 4"). It should have the same specs as this on the label. You'll need two balls, about 100 grams.
You will also need a set of 4.5mm double pointed needles and a set of 5mm needles. I use sets of 5 so that 4 needles have stitches on them and one is the knitter.
The hat will eventually look like this:
I am going to be writing the pattern as I knit it so keep coming back to find out what to do next!