When I started swatching for a new online sweater class with Patty Lyons, I thought my gauge would be pretty close. Boy was I wrong. So I tried the trick where you use a smaller size needle for purling back. That swatch was still pretty far off, especially in row height.
Then I decided to try combination knitting. That’s where you knit and purl back by wrapping the yarn in the same direction, clockwise. Normally we Western knitters purl back counter clockwise, which uses more yarn, making a taller stitch. It’s not intuitive, since I didn’t start out knitting that way, but it really does make a difference in row gauge. My second swatch was almost exactly on gauge for this project. I suspect that it will get better the more I practice. I wonder if this is why garter stitch projects (where you knit back and forth) are so much shorter in row gauge than stockinette projects (where you knit one row, then purl the next row, alternating back and forth).
My next new technique to learn in this sweater: twisted German cast on. Fingers crossed!