Updated to correct row counts and pattern names...
The Harlot just posted that "The [Must Have Cardigan] pattern is intuitive, you'll have it memorized in no time at all."
Well, for bears of very little brain like me, it can take the entire back for you to 'get it' and understand some basic facts about this pattern that can make it much easier.
Step 0: stitch markers. Mark off each section so no stitches get misunderstood to be part of a different section. This made it much easier from the get-go.
Step 1: row counter. I couldn't easily do the patterns without a row counter. You have one pattern (Panel Pattern A) that repeats every 10 rows, with cables on 3 and 7. One pattern (wrapped stitch) every 4 rows--but the wrap happens on row 3 (so every 3 + multiple of 4 rows). And one pattern that has cables on every right-side row, with a total of 26 pattern rows. So very few of the pattern rows line up with one another.
Step 2: Copy your pattern and draw vertical lines next to Panel Pattern A and Panel Pattern B, and write down the row numbers for the repeats through 95 or so (depending on how fast you catch on; it took me through row 87, I think).
Step 3: Understand that the moss stitch is different for every right-side row (knit the Ps and purl the Ks), and same for every wrong-side row (knit the Ks and purl the Ps)... even within the crossing-cable pattern in Panel Pattern B. This helped me a lot.
Step 4: Pay attention to where you hold the stitches for Panel Pattern A's braid. If you put them back instead of front, ugh, frogpond time. I ended up writing "F" and "B" on all the cable crossings for both patterns. That helped a bunch.
Step 5: Realize that after each first twist in Panel Pattern B, when you knit the 3 stitches from the cable needle, the next stitch is always a purl. This works for the moss stitch because you're always increasing or decreasing by a stitch. If you understand that you're always going to be purling after the cable twist, you don't have to look at the pattern--just p1, k1 across till 1 stitch before the 3 knits (on the lower half of the chart) or right up to the 3 knits (on the upper half).
Step 6: Learn what the wrapped-stitch column looks like when it's time to do a wrapped stitch. Then you can stop doing math on the row numbers (hm, is 87 a multiple of 4 rows + 3?). Also, every row that Panel Pattern A cables on is a wrapped-stitch row.
Step 7: On the shoulder decreases, when you're doing 1 dec at each end for X rows, just figure out how many moss stitches you'll have left at the edges (2 sts for size L), put a stitch marker there, and forget the counting. Much easier than ticking off on paper how many decrease rows you've done so far.
I hope this helps someone.