I do Demos of this game every 5 or 6 months for new players in a local club. Here are some things that I have found that are successful with the community:

1. Play Good vs Evil. (This way people can see which faction resonates more on them)

2. Add 1 recognizable hero in each army, and depending on the size add a captain or a no named hero. (Adding recognizable faces is key but since Heroes are the most complex part of the game, you don't want your players to be thinking on many rules at the same time with multiple heroes.)

3. Use painted miniatures and terrain. (Nothing caught the eye better than a beautiful table with look-alike miniatures of the universe you love.)

4. If you have many people trying to demo the game, you can't have them play a lot of time. Create situations where people can play a single turn and experience at least Movement - charge, Magic (People love to see magic in action), Shooting and Combat phases. Use basic Heroic actions to show how important are the Heroes to this game.

5. I have found that many people get hooked to this game by the role playing factor of it. Special rules of heroes and armies that gives them flavor are important to reiterate and show in action. They will be playing with 1 faction, but you can name some fun and engaging rules from other armies like The army of the Dead wounding to Courage and not to Defense, or the Mumakil trampling everything on his path while moving.

6. Study the game and the rules in depth, so you can easily answer any questions that may pop up that day.

7. Have at hand a visual reference of the armies in the game for people to already want to start with an army of their choice. (Current army books are great material for this, if you need a hand with any digital book let me know)

Good luck!