2. Closely related to the math is importance of understanding and taking the time to work with a gauge swatch. Although gauge is not always important in the size of a finished garment, it ALWAYS relates to how much yarn you will be using as compared to the designer. Understanding all the elements of gauge, including making a large enough swatch, blocking and measuring.
3. And speaking of garments, if you are knitting garments one of the best ways to improve your finished projects is to KNOW and understand your ACTUAL measurements. Not the ones you used to have, or hope to have, or think you have, but the real (good or bad) measurements. Which by the way, these must be taken by someone else to have any hope of being accurate.
4. Never be content with just one way. Although we all have our favorite methods of casting on, binding off, increasing, decreasing or finishing those with more options in their "knitting tool box" are almost always better knitters. I would even go so far to say understanding more than one way to knit will help too.
5. Be a life-long learner. There are so many opportunities to learn new things whether in a formal environment like a class or an informal setting like a knitting group. Every one of my knitting teacher friends enjoy the opportunity (when we have availability) to take classes from each other. Just because we know about a topic rarely means there isn't more that can be learned. Elizabeth Zimmerman has been credited with saying, "I believe knitting is a bottomless discipline" and I would have to agree!