A good option to start with is the `-help' (or `-?') option.
GHC spews a long message to standard output and then exits.
The `-v' option makes GHC verbose: it reports its version number and shows (on stderr) exactly how it invokes each phase of the compilation system. Moreover, it passes the `-v' flag to most phases; each reports its version number (and possibly some other information).
Please, oh please, use the `-v' option when reporting bugs! Knowing that you ran the right bits in the right order is always the first thing we want to verify.