How to get help on Windows/DOS commands

Okay, this is one small step for me, and not really any steps for mankind ... I never know how to get help on Windows/DOS commands. I try command line options/switches like -h, -help, --help, /help, and \help, and of course none of them works.

Then somehow today I learned that the magic incantation, er, command line option, is /?, like this:

taskkill /?

Duh.