You've used the ray command so far simply without any command option. Actually ray has around 80 command options that you can insert between the command name and the ending MI file name to control things like output file name and sampling frequency. Most of these options do the same things as corresponding parameters in the MI's option block, but you can use them as convenient rendering switches. There's a couple of particularly useful options:

To display the output image as it's being rendered, use

  ray -imgpipe 1 [MI file] | imf_disp -

To render the file on a network of machines, use

  ray -hosts [host1] [host2] ... [MI file]

Another way to involve multiple hosts in the rendering is to create a text file called .rayhosts which contains the names of the hosts, one per line, and place it in the current directory or your home directory (constructed from the combination of %HOMEDRIVE% and %HOMEPATH%); ray will look for this file and use the hosts specified in there to render the image.