Teaching GIS, what to do and what not to do?
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I agree some of the thoughts already suggested. However to be very clear: do NOT teach the tool, teach the concepts. Yes, it's great that folks know how to use ESRI products (if that is what you are teaching) but give those same people another GIS, and they will struggle--they only know how to use the tool, not think through the process and understand what is happening. If possible, show multiple ways of doing each task, using multiple different tools and methodologies. Have students identify alternate ways of doing tasks... basically get them to think process not tool.
Do NOT show someone something by taking the mouse away and saying, "Just like that". I often teach with projectors and have students follow and then practice on their own.
Allow lots of practice time (if you can...), a rushed course is a crashed course. Teach slowly so that they can take the skills with them when they leave. Not just leaving thinking, "oh, that was interesting, but I still like google earth".
Provide documentation on everything you are doing, especially step-by-step for some of the processes you run through from Data Collection -> Management -> Query -> Analyze -> Visualization.
GIS is a tool, you don't use it, you lose it. So practice makes perfect. The more literal/relevant examples you can teach by, the stronger the concept will be understood, of course.
When I taught basic GIS to an Archaeology group, we did an Arch Site Potential mapping project as example. Or with First Nations, we do land use and occupancy digitizing and some overlay analysis.
I would also add to that comment, but suggest that keywords and concepts will have a longer lifetime than keystrokes and menu selections (ie buffer, clip, intersect, symmetrical difference and their synonyms). If using a GIS with a good help file, get students to focus on how to find the documentation within the software or online. The keywords/concepts will have a longer shelf life...anyone that had to redo their ArcGIS manuals over the summer due to the 9.3.x to 10 translation will appreciate what I mean. Do go slow, videos and screengrabs help (Camtasia/Snagit www.techsmith.com), or network systems that allow you to demonstrate and broadcast to a class (ie LanSchool) also help, but there will be times that picking up the mouse and showing is the only way to do it. There is no one learning style and no single learning speed. Best of luck