It's mostly just not very interesting knitting notes. Since I design most of HF patterns, it's usually that. Stitch counts and measurements and perhaps decreasing sequences.
Ideas or sketches. Needle sizes, yardage, yarns used.
Sometimes I need to keep track of changes made to patterns to make sure sleeves come out the same for instance.
I mostly knit with the same yarns and if I keep notes I can use the same needle/gauge for the same fit. The boyfriend likes one type of hat, so I don't ever have to swatch for that again, I just look through my notes. Boring, I know :)
I am working on 3 new designs though, one shawl, one scarf and a pair of socks, stay tuned!