The 2008 National Electrical Code is an essential reference for studying to pass the electrician's exam.
Electrician's Exam Preparation Guide has hundreds of questions in the same style as actual state electrical exams.
The Interactive Study Center download for the Electrician's Exam Preparation Guide is a lowcost alternative to buying tons of study material.
Electrician’s Exam Study Guide provides 1,500 exam-style multiple choice and true/false questions and answers to help you pass.
This huge 712 page reference from Peerless is a comprehensive guide available to help prepare for the exam.
How to Rearrange Your NEC Pages to Prepare for the Exam

I suggest that you take your NEC to your nearest Kinko’s and have them cut the spine and perforate the center so that it’ll fit into a three-ring binder. Once you have your loose-leaf NEC, remove pages 9 through 21. Reinsert them in the back of the code book, after Annex F. Then go to page 681 and take out pages 681 through 711. Move them to the front of the book, right after the Table of Contents. Now you have the Index and Table of Contents together, where they’ll be most useful.

Now, take some tabs (found in stationery stores or purchased from the link above) insert them in the NEC, and mark the chapter numbers, articles, tables, etc., on them for reference. When you’ve decided which sections of the NEC you’ll be referring to most often, mark those pages with tabs as well. This will make it easier to study for your exam.

What to expect on the Examination
Most electrical exams will include questions on the NEC, general knowledge of electrical practice, theoretical questions, and questions on local ordinances. The questions on the NEC including rules and design calculations comprise from 70% to 80% of the exam.

The people compiling the examination maintain a bank of several hundred questions covering each test subject. Questions are selected at random. The format of the actual exam and the reference material allowed into the exam room may vary with each locality. Typically, an applicant is allowed six to eight hours to complete the exam. Applicants are usually required to report to the examination room at 8 a.m. where the proctors explain the rules of taking the exam. Once the exam begins it continues until lunch -- when there is usually an hour break.

Sometimes it may seem like several of the answers could be correct, but only one of them will be. Use the process of elimination to find the actual correct answer.

Tips on scoring higher
A good way to score highly is to pace yourself. As the exam starts, take a few minutes to look over the number of questions given in the exam and figure out approximately how much time you’ll have to spend on each one. When answering the questions, if an answer you’re not sure of, skip the question and move on. Once you complete all the questions in the exam booklet that you know the answers to, return to the difficult questions that you skipped. When you’ve finished these, take a few minutes to review all your answers.

Using this method should help you increase your score and keep you from fixating on one question while the time passes, and the exam ends, and you aren’t finished.