Thanks for that. It taught me something new, and also encouraged me to look at the man page again. Now, I have the following keyboard shortcuts (the first two came by default):
PrtSc - Capture entire screen; save in ~/images with timestamp; open viewnior to look at the resulting picture.
Alt-PrtSc - Same as above, but with a 10-second delay.
Shift-PrtSc - Same as first, but with the -s flag.
Shift-Alt-PrtSc - Same as first, but only captures the active window.