If they're truly novice, they won't be able to do anything more than just try to keep from draining.
Once they start to get the hang of that, I try to judge the person's interest. Many times, I won't even try to explain any rules. Few people really even care.
The ones that do, I try to point them toward a game with an easy to achieve goal. My favorite is AFM where I tell them to try aiming at the saucer until the bank drops, then keep hitting it until it blows up. Rarely does anyone get past that level of interest.
For fun, I'll try to explain my collection for this beginner-intermediate player. This is not meant to get them high scores or to progress through the game, but only to be something easy-ish to focus on and hopefully get a response from the game.
AFM
Shoot at the saucer
TZ (Not a good beginner game, really)
Shoot the ramps
When the right spiral lights, try to shoot it
Enjoy the gumball machine and hopefully the powerball comes out to create more confusion
Whirlwind (this is surprisingly difficult, considering it's Sys11, so not terribly deep)
Shoot the flashing compass targets
Try to hit the right ramp once it's lit for lock
Most beginners won't start multiball
Tron
Shoot at the drop bank / disk, hope for multiball
Iron Man
Shoot the spinner shots until Iron Monger comes up
Shoot at the Iron Monger
Try not to let the magnet drain the ball
Iron Maiden (Oh, shit! Where to start?)
Try to shoot the ramp in the middle
Flailing will collect enough EDDIE to light a mode
If they shoot the ramp, it will start a random mode, and they'll have no idea what to do, but the lights will be pretty
TNA
Let's play co-op and I'll explain what I'm doing
Shoot at those drop targets
AMH
Shoot at that door until it opens
Shoot the hole behind the door
Laugh when the chain smoking doctor ghost appears