PURPLE - I used a glass bowl and I've used a stainless steel bowl. Both seem to be OK. A lot has to do with what's around in the air and also, I suspect that often as not, you're getting some yeasts that came in with the flour. It's all over and probably the wheat had some, or there was some in the mill, the boxcar, etc. So you may need to try a couple of times. Just make sure your starter stays moist. The flour kind of settles and leaves a film of water on top. When that evaporates, you get a little crust and that's not good.
Paul - I'm not actually sure about overworking the dough, depending on what you're trying to do. One old guy told me that the menfolk used to knead dough because they had bigger hands and could do it harder than the womenfolk back in the pioneer days. I have no idea whether that's true at all, but I knead the hell out of it sometimes. And some of those old Italian women aren't people I'd like to tangle with!
Anyhow, I assume you're kneading by hand. By machine I can't say. The one mistake you can make is kneading too much when punching down the first rising. Once the yeast starts working on the bread, you don't want to knead it any more.
For the same reason if you're kneading away and the yeast starts working but you're still at it, you're kind of working at cross purposes with the yeast and your gluten is going to get overstretched and the bread won't be too good. If you use a fast acting yeast, that can conceivably be a problem.
Too hot for baking right now anyhow.