Depending on the yarn and your knitting style, you might notice that the left-most knit stitch of your ribbing is bigger than the others.
This can happen because you use more yarn when switching from a knit stitch to a purl stitch.
That little black area of the working yarn tends to be longer when switching from a knit stitch to a purl stitch. If you don’t take away that slack it ends up in your knitting.
One simple way to address this is to tug at the yarn after switching from a knit to a purl before you purl that stitch.
You’ll take the slack out of that next stitch and make your tension more even. See:
On the right side, I tightened every time I switched from a knit to a purl. On the left, I didn’t. See how the stitches on the left are a little more uneven and misshapen? This is a way to fix it.
Give it a try!
BTW, if you have another way that you’re already using and it works for you – continue it! Everyone knits differently and if you’ve found a way that works, stick with it.
Also, the composition of the yarn and if you’re working flat or in-the-round can also have an effect on whether the ribbing is wonky or not. But if you’re seeing it on your project and you want to try and address it, give this a go (on a swatch, of course)!