Took the astb in january: sections were english, math, mechanical, spatial, and aviation/nautical background. english and math were the same stuff as you'd see on the SAT. a physics background helps on mechanical(so does being an engineering major), but it's not exactly rocket science. the spatial test has a section right before it explaining how to tell what the picture shows, and it actually helps alot. for aviation/nautical background, learn as much as you can about planes, boats and the ocean.
they are also administering the two biographical sections, but i was told they are no longer used for admissions.
best of luck to you