I was afraid she was going to leave us if we missed any of her questions! :pout: This is a really good place to ask questions and I've never seen anyone get turned away for asking them.
Since we seem to be talking about finding the center of a ball, I'll throw in that I always work from the outside, rather than the middle -- I don't like the way the ball or skein collapses when the inside is taken out.
I could rewind it when that happens, but if I work from the outside, it never becomes an issue.
Since I use either ball-winder cakes or store-bought skeins, I just set it in the top of whatever I'm using to hold my project (tote bag, wicker basket, metal bucket, whatever), and that sits on the floor. As I knit, the yarn unwinds and usually doesn't roll around.
Sometimes I have to give an extra tug, if it isn't coming around the bottom smoothly, but usually I don't have to do anything extra, as long as it is sitting below where my needles are and the yarn is pulled straight up. (Does that make sense? If the yarn is coming off the side, instead of the top, the ball tends to roll and flop around, so I try to keep it on the floor near my feet.)