You know, I never really taught myself to be able to knit without looking. It's just something I started to do without realizing it after I'd been knitting for quite awhile. I think it's similar to learning to drive-you brake and shift gears, etc., without having to think it out each time, but when you first learned to drive, you had to think about it.
I do have a glance though, because I do occasionally split a stitch. However, when I move the yarn to the other needle, I can feel the thickness of it and I can usually tell when I've done this. I can knit and purl without looking, but I don't do lace or anything like that.
Incidentally, I've never been able to crochet without looking, even though I've been crocheting longer than I've been knitting. Go figure!