If you buy any BSD book it'll tell you pretty much any thing you want about how to use the command line - I found that for people like myself who vaiguely knew how to use UNIX, the best book to buy was O'Reilly's "UNIX in a nutshell book", it gives detailed instructions for almoste every command, plus info on emacs, vi, troof scripting and a bit about make files etc... check it out it's worth everything to me!
Dave