My advice to anyone studying for these tests is to buy the 3 study guides that ARRL publishes, but buy them from Amazon at a discounted price, no sales tax, and free shipping if you buy 2 or more.
The books are quite well done. They explain in the various topics what you need to know. The text is footnoted so you know that THIS particular sentence is the one on the test, then they follow up the section telling you to answer questions 2A, 3D, 3E-3G, and 5A, etc. And the questions at the back are reversed X-referenced back to the page in which the explanation is given.
The pool of questions is known up front. All you have to do is know ALL of them!
The online tests, at QRZ.com are good for measuring your progress, but they don't explain the reason behind anything.
Terence, myself, and now Richard have taken the 3 tests in one sitting and passed them with flying colors. It's a lot of effort, but worth it.
Mac