There are multiple SAT tests: SAT II Subject tests - which are usually only required for some elite schools. And, the SAT Reasoning Test, which is the one that is necessary for admission to a 4-Year University.
You can register for it and find a Free Practice SAT Test and a Study Guide at: www.SAT.collegeboard.org
You can also purchase SAT Reasoning Study Guides at your local bookstore.
The SAT takes just under 4 hours and consists of 3 mean sections, one of which includes a 25 minute Essay (they give you a prompt statement, and you write the essay), and multiple subsections - most of which are Multiple Choice. You will have breaks between each of the main sections. The sections are:
Critical Reading - Reading text and answering questions about what your have read.
Math - Includes, Algebra I, Algebra II, Geometry, Mapping, Graphing an Recognizing Number Sequences
English - Vocabulary, Grammar, Composition, and then the Essay.
The sections each score a maximum of 800 points, which, when added together make 2400 for a perfect score. The essay itself is hand scored by two different scorers who must agree on the score of 1 - 6. When you add their two scores together, the maximum score for the Essay is a 12 (and it is then averaged into your English score.