So I use volitional quite a bit to say "I'm thinking about doing X." To do this, I say ~Volitionalと思っています。 Is this correct? I don't know where I learned it, but I seem to use it a lot!
On another note, wanting to review this grammar point but not knowing where it was located, I used the grammar search box on the main grammar page. Unfortunately, typing in "Volitional" yielded nothing. This is probably a wider problem, but shouldn't the English titles in these grammar sections be search-able?
Although I do not think I would call it the negative form. まい is extremely rare, and with the volitional being something similar to "Let's xxx", one would probably not use まい to say "Let's not xxx". A more common approach would be something like ~しない方がいい (It'd be better to not do xxx).