There are five types of buyers:

Need based - They need it now
Strategic - They are always on the lookout for the best offer
Wanderer - The time killer, "Just looking."
Cycle - Typically makes purchases on a reoccurring time schedule
Impulse - It's there, so they buy it.

How do you recognize them?  How do you move an individual to becoming a Need Based buyer from one of the other types?  A solid line of questioning to identify a possible unconscious need is all that is needed.  Think of a time you walked into a clothing store and you bought something you never intended to buy.  It could have been an impulse purchase, or did the sales person uncover an unconscious need for you to buy that item...possibly an upcoming event you forgot about?

“The best way out is always through.” 
-Robert Frost