How to Improve SAT Critical Reading Section Score
To score high on the SAT Critical Reading section, you need to be used to reading SAT-level material and lots of it. You also need to know that SAT reading isn't casual reading nor is it the textbook reading you do for school. When you're reading for the SAT, you have to read actively and understand the main idea of each passage. What you don't need to do is memorize every detail.
Read SAT Passages Actively
As you are reading, ask yourself questions about the passage. What is passage's main idea? What style is the author writing in? Is the passage an opinion? Is it a report? These are all likely questions that could be asked in one form or another. Active reading will help you stay better focused on the passage. Don't get caught asking yourself what you just read!
Staying focused on a passage is, for many, the hardest part of critical reading. This is why practice is crucial. You have to get used to actively reading SAT-level material for a long time. Read from sources like The Wall Street Journal or classic novels whenever you can. Reading a lot will also help you with the SAT writing section and sentence completions.
SAT Sentence Completion
The most valuable tool for SAT sentence completion questions is a good vocabulary. To improve your vocabulary, you can either memorize words from a list or learn vocabulary in context. The best way is the latter method. Why? Because that's how your brain works. You gain a better understanding of a word when you know how it is used. This also forces you to think more about a word.
To learn words in context, read SAT-level material like The Wall Street Journal or classic novels. Surely you'll come across words you don't know. If you don't know a word, look it up in a dictionary and write it down. Do this regularly and watch your arsenal of words grow.
However, if you don't have much time, then you should learn words from a good vocbulary list. Study 30-50 words per day, and at the end of each week review all of the words you have already gone over.