ASTB
Aviation Selection Test Battery
The ASTB is separated into five main sections. They are:

Math Comprehension
Reading Comprehension
Mechanical Comprehension
Spatial Apperception
Aviation and Nautical Information

ASTB Break-down

The following are areas where you can find information, tips, and materials to prepare for the test:

This is a link to study materials for the ASTB:
ASTB Preparation on web

The ARCO Military Flight Aptitude Test book, which can be found at most libraries and bookstores,
is also a valuable asset, especially for the Spatial Apperception section.  It is highly recommended
that applicants obtain a copy.

Below are several links that will aid in you preparation for the test.  
The aviation and nautical terms
are a common problem for test takers not familiar with the Navy/Marine Corps
, so use some of
these links to lean about Naval and aeronautical terminology.

http://www.petersons.com/airforce/pdfsecure/frame.asp?print=yes&pdftype=MilitaryFlight
&bookname=Military+Flight+Aptitude+Tests&sponsor=8

http://www.geocities.com/tiffanypbaker/gouge/astb.htm

http://www.navygouge.com/newstuff/site-map/sitemap.html

http://www.boat-ed.com/wa/course/p1-3_boatparts.htm
More details on the ASTB!