Learn The Classic Force
The magician fans out the deck of playing cards in front of the spectator. This action looks completely casual and impromptu. The spectator selects what they believe to be a completely free choice of card from the pack.
In learning the classic card force you will be performing one of the oldest and most natural forces in a magicians repertoire which can be used as the opening to countless card routines. Once this very useful move has been learned and is practiced, the spectator should choose the magicians force card between 90 and 95% of the time. A well prepared magician should always have a back up trick ready in case another card is selected.
( You could even keep a pinky break under this card to help you keep track of it )
How It's Done: Begin with the card to be forced, on top of the deck.
Now cut the deck so that the force card is near the middle of the deck.
Now hold the pack in your left hand and fan out the cards.
You then slowly spread out the cards by moving them over to your right hand by sliding them over slowly with your right thumb. The real skill in this sleight is timing the point at which the spectator is reaching over for a card. At this moment, you need to make sure that the card to be forced is fanned out closest to their hand.
If done correctly these moves will be so subtle that the spectator will not even realize that these tiny manipulations have happened. You can facilitate this by making sure there is a slightly bigger gap in the fan on either side of the card and even lift the pack up slightly so that the force card touches the spectator's fingers.
Hints: Remember to reassure the spectator that they have a completely free choice of card to reinforce the fact that their choice will be seemingly random.
Practice the classic force moves on your friends and audience at every opportunity, even when a force choice is not necessary. This will give you experience with timing and to boost your confidence by realizing how easy it is to force a card, especially after you have improved your skills with practice
Once again as a precaution, always have a back up trick ready just in case another card is chosen. This way your audience will never know that a move did not work and you can continue to look professional.