Every fingering that fits a hand
3404
easy
3101
open
310x
open
3104
easy
3464
hard
What is true of it
A♯dim is A♯, C♯ and E — 1, b3 and b5 counted from A♯.
The easiest of the 5 fingerings below is 3404: 3 fingers, held at the 3rd fret.
2 of them use open strings, which is what makes a shape quiet to change to.
Where its notes are on the neck
The brass dots are A♯, the root. Everything else is a chord tone with its degree printed in it.
With a different note underneath
A♯dim/C♯
x101
A♯dim/E
x464
An inversion is the same chord with a different note lowest. The name changes to a slash name because the bass is what a listener hears as the foundation.