Well, storyboarding for the two is actually quite different.
Doing it for a graphic novel is rather like doing a rough draft of the story in panel format. Your aim is to get the story across and the general look and feel, as well as possible layout, within the constraints of the page-by-page format. You may not have all the dialogue or action worked out yet, but the style should be represented along with at least rough indicators of how the story flows and sample dialogue.
Doing storyboards for film is a way of starting to outline how the film will be visually represented. Ideally, the story and dialogue are already in place and this is the first visual interpretation of putting those words into pictures. It’s going to be very linear, very streamlined, and artistically not very detailed (at least initially). It’s also handy for planning out detailed FX sequences to give an impression of their look and feel. Film storyboards often include indications of camera angles and direction, again for a starting point for the look of the film. They also aren’t by any mean a shot-by-shot representation of what the film is going to be. It’s an outline, done with pictures instead of words.
Keep in mind for both, however, that styles vary between individuals. So in essence, storyboards are crafted in whatever way makes them most beneficial to you (and your creative team).
Hope this helps!