I did demo's for MW at BGGCon last year. Had a blast. Have the game setup and ready with the apprentice book the game should run about a 1/2 hour(ish). Keep the rules handy but really try to know the answer without referencing the book as much as possible, you shouldn't be splitting hairs. Oh, and if they wargamers, stress that the game is Mage Wars not Creature Wars....you should do fine if you use the guide referenced by Zuberi and by keeping the demo's simple.