As part of your SAT prep, read the newspaper every day (off-line). Mark any words you don't understand and look them up in a dictionary. Highlight the key sentences and phrases that telegraph the author's meaning. You can also incorporate magazines and books, but I prefer newspapers because most articles are short, timely, and written at a reading level similar to what you'll encounter on the SAT test.
Interrogate the text. This is what you'll have to do on the SAT test. Ask probing questions about your reading material. Is the author biased? What does the author imply without stating it directly? What are the author's assumptions? What is the tone of the article - informative? persuasive? entertaining?
Select newspaper articles on things you know nothing about. Don't rely on the sports, fashion, or entertainment sections, but branch out into business, international affairs, and the metro sections. The less you know about the subject going in, the more you need to rely on the article itself for meaning. One of the biggest traps in the SAT Critical Reading section is that people make assumptions that aren't supported in the passage itself. If you bring prior knowledge with you to the test passage, that could prove to be a serious mistake. You must rely on the text, and nothing but the text.
For more information on improving your SAT Critical Reading score, see Resources below or the section on this page titled More Articles Like This.