I went back and swatched again on 4.5 mm needles. Now, I have everything I need to go on to the next step.
On the larger needles, I got a gauge of 9 stitches and 12 rows to 2". That means I have 4.5 stitches to one inch. I've decided to make this hat to fit an average woman, or about 21". So, how many stitches to cast on? Well, let's see...
21 inches multiplied by 4.5 stitches/inch = 94.5 stitches. We'll subtract 10% because we want the hat to be a little snug, not just fit loosely on the head, right? So, 94.5 x .90 = 85.05. That's not divisible by much of anything, an awkward number, so let's round it down to the nearest multiple of 6. That would be 84 stitches. Why a multiple of 6? Just cuz I like the way the top of the hat comes out when it's done in 6 sections. And, it's a nice even number.
So, now that we have our number of stitches to cast on, we can start. Using the 4.0 mm needles, cast on 84 stitches. Join in the round, being careful not to twist the stitches. Place a marker to mark the beginning of the round and rib (I chose 1x1... or knit 1, purl 1... rib) for about 1.5", or whatever you'd like.
Then, change to the larger (4.5 mm) needle and work 2 rounds in stocking stitch (just knit). Now it's time to start the fair isle patterning. We'll get to that tomorrow, with pictures.