Introduction
In magic the term glimpse is applied to the act of sighting and taking note of any particular card secretly. There are many ways of doing this; some of the methods have graduated into the conjuring class from the gaming table and require considerable skill to execute properly. The best of these will be considered later. In the meantime let us take up first the one that is most easily acquired.
Bottom-Card Glimpse
Bottom-Card Glimpse I
We shall suppose that you have handed the deck to a spectator to be shuffled. When he has done that, hold out your right hand to take back the deck, purposely holding it rather high so that he will have to raise his hand to give you the deck. Take the pack with your thumb underneath it on the face card, your fingers on the back. At that moment it is natural for you to glance at the cards, and by tilting them ever so little with the thumb you can glimpse the index of the bottom card at the inner left corner (Fig. 43). 
Immediately look at the spectator and address him with some such short remark as this, “You are satisfied that you have mixed the cards thoroughly?”
Do not tilt the pack so far that the whole of the face card is visible to you. Slope it just enough to see the index only. Also do not turn your gaze toward the pack as you tilt it; you should be looking at the pack only as you take it. Get the glimpse and then look at the spectator. Make the action a natural one, and no one will have the least suspicion that you have seen the bottom card. [Note: The key to effective glimpsing is naturalness – the action must appear completely innocent and be disguised within normal handling of the cards. The brief eye contact with the spectator creates psychological misdirection. – RJW]
Immediately after making the glimpse, execute an overhand shuffle, controlling the sighted card by keeping it at the bottom or sending it to the top of the pack.
Sometimes the spectator will play into your hands. Many laymen make the shuffle roughly, and often you can glimpse the bottom card either as the shuffle is made or as the cards are being squared after the shuffle. Always make a point of watching for this. If you do not sight the card, then resort to the method explained above.
Bottom-Card Glimpse II
This is a bold method but a good one.
Offer the pack for shuffling and when it is returned hold it face downwards at the ends between the right thumb and fingers. Say: “Kindly notice–nothing up my sleeves,” and draw back the right sleeve with the left hand. As the right arm is extended, tilt the pack enough to enable you to glimpse the index of the bottom card. [Note: This method uses misdirection through the classic “nothing up my sleeves” gesture. The bold nature refers to the fact that the glimpse is taken while seemingly demonstrating fairness, which actually makes it less suspicious. – RJW]
Bottom-Card Glimpse III
Offer the pack for shuffling and when it is returned hold it in the left hand as for dealing, face downwards. Thumb off about a dozen cards from the top and take these in a fan in the right hand, letting it be clear that you do not see the faces.
Hold the hands well away from your body as you say, “You will certify that these cards are well mixed?” Run your left index finger over the faces of the fanned cards, from right to left, with the back of the hand toward yourself (Fig. 44).
Note the bottom card of the pack, which faces you, and instantly avert your gaze. Your eyes must not dwell on the card but flick it in passing.
Replace the fanned cards on the deck in the left hand.
Top-Card Glimpse
Take the pack in the left hand, as for dealing, but with the index finger curled up over the outer end and the thumb lying flat against the left-side edge.
Gesture to someone, saying, “Will you help me?” As you make this gesture, turn the back of the hand uppermost, bringing the deck face upwards. Push the top card to the right with the left fingertips; this will expose the inner index (Fig. 45). 
Return the hand to its original position.
Riffle shuffle the pack, retaining the top card in position but making sure that the original bottom card is lost near the bottom of the pack in the event that someone may have noticed it and may be following it.
Fan Peek
This is a method of ascertaining which card a spectator chooses from among a number of cards.
Hold the cards vertically and thumb them from the left into the right hand, inviting someone to touch any card and remember it. Place the left thumb against the lower edge of the card he touches, at the index corner, and drop the hands somewhat, never glancing at the cards.
Raise the fan again, saying that you wish him to be sure to remember his card, and instantly raise the index corner with the thumb, glimpsing the index (Fig. 46), and remove the thumb. Close the pack and hand it for shuffling.
Wherever possible a chosen card should be glimpsed by one or another of the methods given above as soon as possible after its replacement in the pack. In the event that the card is accidentally lost, or if a spectator insists on being allowed to shuffle the cards himself, knowledge of what the card is still leaves you master of the situation.
[Note: This fundamental principle of card magic – gaining knowledge of the chosen card as insurance – is crucial for maintaining control of the performance even when things don’t go as planned. – RJW]
For other methods of glimpsing, refer to the Palm Glimpse and the Double-Lift Glimpse.