Sweater so far:
Pick up 54 stitches around the armhole opening.
The stitches should be arranged as follows: 2 stitches over cast-off stitches at underarm, 26 stitches to shoulder, 26 stitches back to underarm.
Sleeves are worked in the round, with no underarm seam.
Begin work in pattern stitch at the 2 underarm stitches. The two underarm stitches will be "purl 2" of the pattern and a "knit 4" rib will be centered at the top of the shoulder.
On the first round, P1, place marker, continue to end of round. The marker is at the center of the underarm.
Work pattern stitch for 5 more rounds.
Begin sleeve decreases on next round Decrease one stitch on each side of marker, every third round.
In other words, decrease 2 stitches at underarm every 3 rows, 12 times. (30 stitches remain).
(Hint: I found it easiest to keep those two underarm stitches as "purls"...one on each side of the marker, adjusting the next stitch away from the marker as the pattern gets decreased away)
Continue to work even in pattern stitch until 7 complete pattern repeats have been worked (7 purl ridges), ending with row 6.
Change to smaller needles and work 6 rounds in P2, K4 ribbing.
Bind off all stitches.
Work second sleeve to correspond to first.
Weave in all yarn ends.