Need help with 'du' command

[Dr. Jones]

If this is not the right place to ask this, please point me in the right
direction.

I want to do the following:

List the size of each primary directory off / root, listing the size in
human readable form, i.e., /usr 400mb /var 1.2 gb and so forth, without
listing every file, or every subdirectory.

I have tried various combinations of all the arguments outlined in
the --help file, in the man page and from reading through the INFO document.

Thanks for any help with this.

Scott