|Gauge swatch, in action.|
This question came up in an Amazon review: "How many people can make a first anything...fit perfectly when it comes to knitting?"
It is true that perfection isn't possible in a lot of things. Your first omelet won't be perfectly beautiful. The very first thing you knit probably wasn't perfect.
But, I'm going to risk myself and put it out there. If you:
1) are careful when you measure
2) work a gauge swatch
3) follow directions well
...you CAN have your very first pair of hand-knit socks fit you. Perfectly.
Yes, practice helps. If you knit the same size of socks in the same yarn on the same needles, you'll learn when 2 or 4 stitches or rounds one way or the other really matters and when you can fudge it.
I also really, truly, completely believe that you have to knit a gauge swatch whenever you have a new sock size, yarn, or set of needles. That is, if you don't want to add to your "this was a nice pattern, but the socks don't fit" pile.
It is part art and part science, but it's not impossible!