I am starting with spherical panorama's, i am using the following ;

nikon d200
tokina 12-24
Nodal ninja mk3 + rd8 rotator.

I have some questions,,,,

1. Must i use the AF mode, or do manual focus ?
2. if i use manual focus, where to focus ? (close or far away)
3. What diafragma to use ?
4. sometimes I see examples of a spherical panorma, with people on it ! How do they do that ? (or do i just need a more fisheye lens ?)

I saw a sigma 4.5 mm for sale, is this a good lens for making spherical panorama's ?