If you're just starting out, or don't know what I mean by "reading" your knitting, let me first direct you to these two excellent series of blog posts:
"Reading" Your Knitting (Parts 1, 2 & 3) by Talena Winters
The Secret to Becoming a Great Knitter! (Parts 1, 2 & 3) by Felicia of the Craft Sessions
These are great starting points for mastering this skill. The best way to learn to "read" the stitches you are or have knitting, however, is practice. Keen observation of what the yarn is doing in your hands as you complete each knitted stitch, decrease, increase, yarn over, cable; what these stitches look like as you progress (what do they look like right after they've been made? what do they look like a few rows down?); these are the puzzle pieces that will make this skill come together for you.
I've given a lot of thought to how I would teach this in a workshop situation, and although Yarn Club meetings aren't workshop-length, I thought I might try out my idea amongst our friendly and open minded group.
The Baby Sock Reading Challenge
The idea is simple enough: You make one baby sock without instructions, and without taking notes. Then you make the matching sock by looking at the first and deciphering what you did from its stitches. If they don't end up matching exactly, well, they're just baby socks and you haven't wasted much time trying. And maybe you've learned something (such as how to accurately count rows, or how to make a sock without a pattern, or that you CAN read knitting and didn't realize it, or that you absolutely HATE knitting without precise instructions...). Obviously my hope is that you learn to recognize that reading knitting in this way is a possibility, and one that can take your knitting to the next level, with time.
To illustrate my challenge, I made a baby sock, and went through how I would go about reading it to make the second. I also wrote out my Patternless Sock Guidelines, to help start you off. You'll find many other great sock "recipes" on Ravelry as well, such as this one from Susan B. Anderson.
Knowing the cuff rib repeat makes counting the stitches easy. Mark your starting point with a needle (or in my case a thumb - remember, lazy!) and count around by twos for a [K1, P1] rib as here.
I use a very low profile cast-on for my sock cuffs. The Double Twist Loop Cast-On is quick and stretchy, and doesn't interfere with row counting. You can see the red outlining the cast-on in the image above. Count the rows up from your cast-on edge by counting the little Vs that occur above the cast-on and before the beginning of the stitch pattern.
If you choose a stitch pattern with an easy repeat (I used Double Moss Stitch) you can count the leg rows in number of pattern repeats, rather than individual rows, which can make things faster, particularly if you're working on an adult-size sock.
Slip-stitch patterns can be difficult to learn to recognize, but the trick is to watch for the larger stitches that span the height of two smaller stitches. These elongated stitches are the ones that have been slipped. In the Eye of Partridge slip stitch pattern, the elongated stitches appear in a checkered pattern with the groups of two smaller stitches in between.
Count the heel flap stitches in the same way you would the cuff stitches - in the case of my Double Moss Stitch, by twos. Alternately you can count the slipped-stitch pattern by single stitches and add the selvage stitches on each side to the count.
I use two or three garter selvage stitches on each side of my heel flaps. Not only does this make stitches easier to pick up along the edge, it also makes it easier to count how many rows I have worked in the heel flap.
You can see the decreases stitches overlapping in the turned heel which is your clue to it being a short-row decrease heel (as opposed to a straight short-row heel, which would have visible wrapped stitches).
The number of stitches between where decreases begin is your heel's "turning point." See my sock guidelines for a heel turning point explanation.
If you make an identical heel flap to your first sock, chances are you'll be picking up exactly the same number of gusset stitches anyway. You can count them easily enough, but know that if you have an extra stitch in there, it's not going to make much of a difference since you'll be decreasing to the original number of stitches anyway, and if it seems like you NEED that extra stitch in there this time (to avoid a hole for example) it will probably look better with the stitch than without it - stitch counts be d***ed.
You can identify a decrease pattern by looking for the decrease stitches (the ones leaning over a little extra) and also counting the rows in between those dec sts. Above the dec sts are identified by the red dots, and you can see there's a regular stitch between them as the rows progress. So, the decreases are being worked ever other row.
I count the foot length in single rows from the final gusset decrease to the first toe decrease because they line up, and because that final gusset decrease might happen halfway through a pattern repeat on the instep, which makes it more difficult to count.
In order to make a nice round flat toe, the decrease pattern needs to be a little more complicated than the gussett decrease to achieve the gently increasing curve. Just as with the gusset decreases though, you simply identify those extra-leany stitches, and count the resting rounds between them. I think of them expressed like this: D, 2, D, 1, D, D, D - wherein the D stands for a decrease row, and the numbers stand for the number of resting rounds between them.
Counting the sts grafted at the tip gives you half the final stitch count. For instance, if there are 5 grafted stitches forming the toe tip, you know that there were 5 x 2 sts = 10 sts total to form that graft, and therefore 10 sts left on the needles when the knitting stopped.
Et voilà! Now I just need to finish the other one...