Knitting

Yeah, your "how many decreases per row" problem on the inward-knitted squares depends on the stitch you're using, and your particular knitting style. If your stitches were perfectly square, three->one in each of four corners would work perfectly. Two rows of garter is close enough to square for most people for this to work every second row. But for other stitches, you have to adjust so you decrease often enough, but not too often. Every two out of three sounds, like medrin says, a good one to try with a typical stocking stitch pattern. If you've got ribbing or lace or anything else, you'll need a gauge swatch and a bit of maths. (Which I will happily help you with if that's an issue.)

And from my experience with hats, yeah, the 12-stitch row is probably the one to bind off on unless you're fond of nipples.