Do a "Northwest Tackle Box" approach--one for fly and one for everything else (non-fly). Pick, for example the top ten non-fly fishing presentations, talk about the lure/rig, and how and where it is best presented (mepps spinner, slider bait rig, curlytail grub jig, etc). For fly fishing, three or four basic patterns, sink tip/float tip, and some emphasis on casting. If these folks are beginners, getting them into a fish or two quick is important, even if it's a perch or 10 inch stocked trout. Then they'll hook themselves, and you won't even need to set the hook.