I am thinking about starting to try to make my own vegetable stock. I have a few questions though:

1. Is there a proper water to veggie ratio when making it? I know, of course, that the longer you cook it, the more concentrated it will be, but is there a place where you are supposed to stop?

2. Is there any veggie that you can't use for stock?

3. One of the things I want to use in my stock are all the veggie scraps I have leftover (carrot peels, onion detritus, etc). Are there any scraps that aren't good for stock (such as the core of cauliflower)?

Thanks!