For Out of this World, I use a method based on a combination of John Armstrong's and Eugene Burger's handlings. I also use postcards based on Chris Philpott's French Postcards - but mine have more Rated - G, audience friendly pictures.
For a presentation with a deck of cards, I would do something like this:
What do you think the difference is between coincidence and luck? [Listen to answers and react by laughing if they say something funny, by commenting "good answer" if they say something thoughtful, or even "that's right ,but it might be just a luck guess"]. Does anyone feel lucky? [Someone responds yes, or you further prompt someone "do you feel a little lucky today?] OK, I'm going to have you help me out here. Now, does any feel that the universe is aligned to provide them with some coincidences today?" [Someone responds yes or you further prompt someone "do you believe in coincidences?" if they say yes you continue, if they say no, you say "either do I - what a coincidence" and continue]. OK, I'm going to have you help me out in a minute.
[Talking to first participant]. We are going to test your luck. As you can see, the card are well shuffled (spread deck showing cards shuffled). I'm going to hold each card face down and you tell me if it's a black card. If you think it is a black card, we will put it in this pile here [gesture to the space between you and the participant] and if you think it is a red card or aren't sure I'll put it over here [gesture to the side of you]. Let's test your luck. [go through cards dividing into piles].
[Turn to second participant] So let's test the power of coincidence against sheer luck. I'm going to hold each card face down and you tell me if it's a redcard. If you think it is a red card, we will put it in this pile here [gesture to the space between you and the participant] and if you think it is a black card or aren't sure I'll put it over here [gesture to the side of you]. Let's test your luck. [go through cards dividing into piles].
So who do you think got more cards right? Luck or coincidence? [Turning to first participant] Do you feel lucky? [listen and react to answer]. Let's see [spread cards in middle showing all black]. That looks tough to beat. [Turn to second spectator], do you think you had as many coincidences? Let's see [spread cards in middle showing all red]. OK, let's go to the tiebreaker, let's see how many you discarded that you should have kept. [spread discards showing all red followed by all black]. [To both spectators] Regardless of whether it was luck or coincidence, well done, both of you.
Notice a couple of important parts to the presentation. First, it starts with questions to the audience, engaging them. Second, it introduces the theme of luck vs. coincidence and carries that throughout. Third, there is no attribution of magical powers or skill to the magician. That keeps the audience from playing the "my job is to figure out what you are doing so I can put you down a peg" game. A the end, the credit goes to the spectators.
You can also have some interplay with the spectators. Ask them if they are sure when they put one in the discard pile. If they hesitate, ask them if they want want a friend to help them (and then comment if they get one wrong they know who to blame). You can ask another spectator if they agree with a decision. You can let them check one card if they seemed unsure. That interplay keeps the rest of the audience engaged and also disguises the method because none of that would be necessary if it were a foregone conclusion that they would get all their choices right.
Feel free to post a presentation you've come up with for another effect or to throw another effect out there for me. Others, should feel free to post their presentations.