Biennial Flight Reviews
What is a Biennial Flight Review  (BFR)?
Can you fail the BFR?
Since the BFR is an instructional session, you cannot "fail" it as such.  However, if the CFI determines that you are not safe to fly, i.e. your knowledge or flight skills are inadequate, he has the option to not sign you off until you receive further instruction and can demonstrate that you indeed have mastery of the aircraft and have the necessary aeronautical knowledge.
What does the oral portion consist of?
There are four ways to meet this requirement: 

One - sit with the CFI and answer all questions, and discuss any item of which you are not sure.  This the LEAST recommended method, and in fact some CFIs will NOT do this any longer.

Two - Take the on-line course.  This is a good and viable method, as you learn a lot more than any other way.  You can keep reviewing it until you understand all of it - you cannot fail it.  At the end, you print out a certificate of completion which you show to the CFI at your BFR, and that takes care of your oral portion.  Cost is $29.95, which is much less expensive than a CFI's time.  Here's the link:

Three - attend one of the many FAA Safety Seminars in person, and receive credit for it.  Print out the email from the FAA which certifies that you attended the session, and show that to the CFI to satisfy the oral requirement.

Four - this is the easiest. Take one of the many FAA's WINGS courses online.  It's free, and takes about 45 minutes.  You'll get a certificate at the end, show that to your CFI, and the "Oral" portion of your biennial flight review is done. You'll have to create an account, which takes about 30 seconds.  Here's the link:
Every  FAA certificated pilot must demonstrate that he/she continues to maintain the  aeronautical knowledge and flight skills necessary to safely operate an aircraft in US airspace.  This is accomplished by receiving two hours of instruction provided by a certified flight instructor at least every two years.  The session consists of two portions - one hour of oral question/answer period, and one hour of actual flight time (flight line and in the air).
What does the flight portion consist of? 
The CFI will specify a series of flight maneuvers designed to demonstrate your mastery of the aircraft.  "Mastery" simply means that your aircraft does exactly what you intend it to do.  Unlike in a practical exam (checkride) given by an Examiner, during a BFR you can repeat a maneuver if it is not satisfactory.  In fact, the instructor can take the time to correct you, show you how to do it if necessary, and have you do it until you get it right.  

The flight portion also involves showing that you know how to use your checklist, use runways correctly, use correct radio terminology, and properly conduct other pre-flight and post-flight activities.
Other important notes:
*  You can take the BFR in ANY aircraft in which you are rated.  So if you are rated in single engine fixed wing airplane, a Powered Parachute, and a rotorcraft, you can take it in any of those and it will suffice for the next 24 months and count for ALL of your ratings.

* You can also satisfy the BFR requirement by receiving a new category/class qualification (add Sport Pilot LSA to your Private license, for example).

* The 24 month clock starts from the time you complete the BFR.  You MUST receive another BFR any time within the next 24 months.

* If you do NOT have the BFR completed within the prescribed time frame, you are not CURRENT, meaning that you cannot legally fly any aircraft.  It is equivalent to having your driver's license expire, for example.
How do I set up a BFR session, and what does it cost? 
Contact a CFI (see "Instructor Staff" tab on left ) and schedule a date/time.  It's that simple.  Bring your logbook and your aircraft (with the necessary paperwork, airworthiness, registration, etc.).

The cost is shown on the "Costs" tab on the left.