What to say
Basics
Put the subject at ease. Try to be friendly, and approachable. Mentioning that reading is a team effort should help.
Remember that most people love to hear/talk about love, health, money, careers, travel, education, and ambition.
Start vague, then hone in to more specifics.
Phrase your questions as statements.
Rephrase the answers to questions back to the subject.
Pacing is important. Try to speed past misses, and linger on hits in the questioning.
Tell them what they want to hear. Flattery can go a long way.
Generalizations
Weekly horoscopes are a great source for generalized statements that can be peppered into any reading. Keep statements so general that they can apply to anyone. Remember that people will remember the coincidence of what you say, applying to their lives, and forget when no coincidence arises.
When asking questions you also want to be as general as you can. Opening with something like "You've lost someone close to you?" will have a better chance of the subject filling in who they've lost, than risking a false start with "You've lost your father."
Barnum and Rainbow Statements
The two most common classifications for statements that cold readers use are Barnum statements, and Rainbow statements
Barnum statements are named for P.T. Barnum, who is often sited as the source of the line "There is a sucker born every minute." These statements are generalized lines that can apply to almost anyone, but worded in a way that sound specific to the subject when said.
Rainbow statements, while being a bit less general, usually hit two ends of a spectrum so that they can also apply to anyone.
Here are some good examples of Barnum and rainbow statements that you can pepper into any reading:
"You have a great need for other people to like and admire you"
"At times you have serious doubts whether you have made the right decision or done the right thing."
"You tend to be too self critical."
"You're an independent and creative thinker."
"You do not accept what others tell you to believe."
"Some of your goals seem to be a little unrealistic."
"While you're often very generous and kind, you occasionally have a selfish streak that you feel a bit guilty about."
"Though often times you are outgoing and social, sometimes you feel like being in isolation."
"You are a generally very nice person, but when someone does something to break your trust, you feel a deep sense of injustice that is hard to hide and hard to let go."
"You are normally somewhat reserved, but occasionally you like to be in the lime light."