A couple years back I actually learned a few card tricks and strung together a bit which I succesfully performed once or twice before life in general pushed me away from magic.

So here for your ridicule/praise is the script of my first routine ever.

Setup: The magician comes up to Mark, the spectator, and has him shuffle the deck. He then takes the deck back, has Mark take the top card and show it to the audience without the magician seeing and replace it at the top of the deck.*

*Magician shuffles the deck and pulls the top card from the deck, which is not Mark's card.*
Is this your card? ... It isn't? Er... ok let me try again.
Magician shuffles the deck, and has Mark pick another card, which happens to be his original card. Magician shuffles again and once more fails to produce Mark's card.*

*The above scene plays itelf out one more time*
Magician: (frustrated) "I give up."
*Magician sets the pack down face up to reveal that Mark's card is at the bottom of the pack as he walks away muttering about what went wrong.*

Strangely, it worked out fairly well.

Sounds very effective!

I use a similar routine when I work with cards. I tend to have the same card selected (eg 4H) everytime anyone selects a card. I do this out of habit, and for the practice. It can really get the audience going.

Most of my tricks do not use the 'pick a card and I will tell you what it is' theory, so it doesn't matter that the audience knows that I always know their card. May not work well in other routines.