Print out a copy of the checklist below. Laminate it, place it near the printer, or give a copy to each of your students. If you run through the list each time you print, you should be able to avoid most common printing mishaps.
When you have a model
Have you checked to see if your model is error free?
Did you start with default settings? If not why not?
Does your model have a flat surface to place on the platform?
Did you place your model flat on the platform?
Does your model need support material?
If you need support, did you select Touching Build Plate or Everywhere?
Do you want a raft, brim or skirt?
Are you printing "all at once" or "one at a time"?
Are you slicing for the right machine?
Did you slice for the right nozzle diameter?
Did you specify the layer height appropriately?
Did you specify the wall thickness and line count?
Did you specify an appropriate infill density?
Did you name your G-code file to associate your model with you?
Before you press print
Is the platform clean?
Is the platform level?
Do you have enough filament?
Is the type of filament you want on the printer?
Do you have enough time to complete the print?
After you press print
Did you see the first few layers print before walking away?