A control question is one where you are required to give the "correct" answer.  Whether your answer is a lie or not depends on the way you define the question.

Have you ever committed a serious crime?
(I don't know... what is a serious crime?  Is a DWI a serious crime?  Is jaywalking? My mother thinks that missing church is a serious offense against God).

As opposed to: Have you ever been arrested? This is a straightforward question and requires no further clarification.  

Are you trustworthy?  Do you think that answering "Yes" to that question is a lie?

1. Have you ever lied to a supervisor?
2. Have you ever lied to loved ones?
3. Have you ever lied to parents, teachers, or the police?
4. Have you ever lied to get out of trouble?
5. Did you ever reveal anything told to you in confidence?
6. Did you ever cheat in school?
7. Did you ever cheat in college?
8. Did you ever betray the trust of a friend or relative?
9. Did you ever steal anything from an employer? (Note, however,
that any question about stealing money from an employer is a
relevant, not a control question!)
10. Do you sometimes intentionally mislead or deceive your
friends?
11. Are you a really honest person?
12. Are you absolutely trustworthy?
13. Do you think you are smarter than most people?
14. Are you an untrustworthy person?
15. Are you a dishonest person?
And if you consume alcoholic beverages and drive a car, you may
well be asked:
16. Have you ever driven while under the influence of alcohol?
This may seem like a relevant question, but it’s not. Your polygrapher
assumes that anyone who drinks and has a driver’s license must
polygraphy exposed 101
have difficulty to honestly say he’s never driven while under the
influence of alcohol.
Other “control” questions commonly used in probable-lie “control”
question “tests” that may at first seem like relevant questions
are:
17. Is there anything in your background that you are afraid that
our investigator might find out?
18. Have you ever done anything that would embarrass you if
your parents found out?
19. Have you ever done anything you would be embarrassed to
tell me about?
In addition, if, like most people, you initially admit to having told
some white lies, your polygrapher may rephrase the question as:
20. Have you ever lied about anything serious?
Don’t be fooled. It’s still a control question. Your polygrapher expects
that your denial will still be a lie, or that you will at least feel anxiety
over whether your denial is completely truthful. Similarly, if your
polygrapher rephrases, “Did you ever cheat in school?” to “Did you
ever cheat in college?” it’s still a “control” question.

And yes, if the CQ response is higher than the RQ response, you will fail the test.  This is why the more honest you are, the more likely you are to fail the polygraph.

OMG, I made a MAJOR typo and nobody corrected me...
This is supposed to read: "And yes, if the RQ response is higher than the CQ response, you will fail the test.  This is why the more honest you are, the more likely you are to fail the polygraph."
My mistake was obvious in the context of the previous post, but I sure hope I didn't confuse anybody.
I'll correct it now.