Flight Review (BFR)
The following are excellent paper and online resources when you are preparing for a flight review:
Bob Wander
Book: "Safer Soaring...Made Easy"
Book: "Glider BFR and Spring Checkout...Made Easy"
Aircraft Owners and Pilots Association (AOPA)
Federal Aviation Administration (FAA)
Online: Flight Review Prep Guide
The above link will bring you to the FAA's online list of courses.The "Flight Review Prep Guide" course is an excellent summary of the part 91 regs as well as judgement based decisions. The content is oriented towards powered aircraft but most of it applies to glider flying. There is an exam at the end that allows you to answer the questions over and over until you get it right. Getting the correct answers is the only goal of the exam. You don't have to pass on the first try to get credit.
Preparation Example
Your Instructor may have a different request but here is an example of good preparation for a flight review. Study each of the following resources:
Before your Flight Review grounds session, acquire and study at least one of the Bob Wander books listed above.
Before arriving for your flight review ground session, complete the SCOH specific Flight Review questions.
Acquire a current sectional (LINK). Optional but even better than a sectional is to use your iPad application, Foreflight .
Acquire a current FAR/AIM (LINK).
Extra Credit: complete any of the above AOPA or FAA online courses.