Discovering and building on employee strengths is a vital and important way to generate business success. Marcus Buckingham's book, "Now Discover Your Strengths" builds on the insights Peter Drucker had forty years ago, but it leaves two crucial things.
First, it's just as important to make weaknesses irrelevant as it is to discover and build on strengths. You can make a weakness irrelevant in several ways.
Eliminate the weakness through training or development. Understand that you only need to train to a "good enough" level. Most of the time you can't develop a naturally-weak area into a great strength.
Eliminate it by developing habits, rituals, or routines. A person who's not good at remembering things like birthdays can use a reminder service. A person who's a bit disorganized can use a daily checklist of things that have to be done. This has all gotten a lot easier with PDAs and web services.
Make it irrelevant by outsourcing it. Have a salesperson who's awful at reports get an assistant to help get them done right and in on time.
Determine whether the job needs to be done at all. Business histories are filled with folks cranking out reports that no one reads anymore because the original need is gone.
The other thing that the book misses is that there are ways to identify strengths without taking Buckingham/Gallup's instrument. The instrument is good, but consider some other options, too.
Simple observation works wonders. My research on Three Star Supervisory Leaders found that a characteristic behavior is that great leaders show up a lot. Showing up a lot, coupled with observation will tell you a lot about what your people do well.
Ask. Most people know what they're best at. But be sure to also ask, "What do other people always tell you you're good at?" Ask people who know the person directly, too.
Other books, tools and instruments can also help identify strngths. Consider any of the variety of tools based on Jung's Personality Types, including Myers-Briggs Type Indicator and the Platinum Rule instrument.