Every class I teach is different. The students are at different levels; they have differing degrees of experience and confidence in their own skills.
But it's pretty universal -- all "beginner" knitters seem to have one thing in common. They don't look at what they're doing.
They're concentrating on each stitch, on reading the instructions, on holding the needles -- they're concentrating on the knitting, but not on the knitting. I looked at the work of a couple of my students this week and there were some really very obvious mistakes. For one student, it was purl stitches where there should be knits in a number of places. For another, a wholesale change of sides so that what was stocking stich became reverse stocking stitch.
And in both cases, they hadn't noticed the mistake, they said, until much later.
I read in a book, once, a long time ago, that a good knitter stands back to admire the work in progress, on a regular basis.
I tell all my students to take a good look at what they're working on. Hold it up. Examine the pattern stitch. Make sure that you're working the right direction.
I've seen fronts of sweaters with the armhole shaping only done on one side ("Oh, so that says 'at beginning and end of the row'"?) . I've seen stocking stitch reversed mid-way through a piece. I've seen purls where there should have been knits. Cables that haven't been crossed. Mis-aligned ribs.
Hey, I've done many of these myself. Every knitter makes mistakes. Even experienced ones. The difference, it seems, between a beginner and a more advanced knitter is how quickly the mistake is spotted.
Fixing mistakes is another set of skills entirely, of course. But you start by knowing where a mistake is.