Well, This is what I know:
When I knit the Back...I place thread markers every 10th row...or if it's a cabled project...I place a thread marker at the top and base of every repeat. I place the thread in the st st part of the sweater.
I keep measuring from the ribbing up to the armhole bindoffs. Let's say you are supposed to start binding off for the armholes at 19". When I reach 19"...by counting the cable repeats...I will know exactly what repeat and what row within that repeat reached the 19" requirement. I'll make a note (in my notebook, under "Back") that 19"=10 repeats/4 rows. My shorthand will look like this: 19" (10/4)
Then, my notes will say: Begin armhole shaping. Bind off 4 at the beg of the next two rows: 10/5 & 10/6. I will place a different color thread to mark row 10/5, where the first bind off occurred. (if I was using red to mark the repeats, I'll use black to mark this row 10/5 for the beginning of the armhole)
Now let's get to the armhole length before beginning the shoulder shaping bindoffs.
The directions might say to work so many decreases on the armhole edge (for fronts there's only one armhole edge, for the Back there are, of course 2). Then the directions might say: when all decreases are satisified, knit even (meaning "no further decreases) until the armhole is 9" from the armhole bindoffs.
I already know that the armhole bindoffs occurred on Rows 10/5 & 10/6 (using the Back for our example). So, when I think I am approaching the 9", I'll start measuring from that black thread marker (which is keeping track of the armhole bind off row). When my work on my needle is 9" from that black marker, and on the next RS row...I will begin my shoulder shaping bind off sequences.
I always work the Back first. I measure carefully for the Back, and keep good notes about what repeat and row that significant things occurred. I don't take those markers out until I am ready to block the entire 5 pieces. You never know when you will have to refer back to them.
Anyway, back to business. Next, for my two Fronts I don't really have to measure again. I just keep track of the repeats and rows...and do all my bindoffs and other significant things on the very same repeats/rows that I did for the Back.
For example, for the Left Front...when I get to Repeat 10 Row 5 (10/5)...I WILL MEASURE, just to verify the 19" requirement...but usually it is spot on. If not, then I investigate if I counted my repeats and row right. If I did the repeat/row markers right, I double check my row gauge. Maybe it took me a long time to start the Fronts. Maybe my row gauge is off. Also, be sure that you are not distorting the knitting when measuring.
Anyways, I hope I've answered your question, and also thrown in a couple of my own knitting tips.
I do these row markers for every project I knit. It really helps keep things on track.