Many law school admissions committees value a student's personal statement as equal with GPA and the LSAT score!
It stands to reason then that careful study and preparation of your personal statement is a critical part of preparing to enter law school.
The Princeton Review publishes a book titled Law School Essays That Made a Difference. The book is now in its 4th edition.
This book includes law schools students applied to, successfully and unsuccessfully, and the complete texts of their personal statements.
The book also discusses the process of law school admissions, has interviews with law school admissions officers and a rather extensive discussion about how to write a personal statement.
The 4th edition should be in every budding attorney's library and you can purchase it here.
The 2nd edition is available in the Phi Alpha Delta library.