Hmm, how do you imagine that?
A option in the main menu that opens a tutorial mode and launches you into a predefinded level.
Then, some text messages start instructing you on what you should do, maybe with army-like messages, i.e:
* Ok, marine, start moving! (Use the Numeric Keypad to move in all 8 directions)
* Explore the area and report back. Good luck, soldier!
Then when you approach certain zones, more messages would appear:
* Shoot that training dummies, soldier! (press f to shoot, NumPad to change firing direction)
* Pick up this shotgun (press g)
* Your weapon has emptied, marine! Reload! (press r)
* Close the door! (press c)
And so on. It might help to get people into something that, at first glance, appears impossible, don't you think? ;)