I'd have to agree with Lala that Powerscore is the way to go. But if you are doing "awful" as you say, my guess is it had more to do with your strategic approach to each Q-type.
I just posted these CR tips elsewhere, but I thought I'd share them with you as well!
CR TIPS
Always identify and WRITE DOWN the Conclusion, Evidence & Assumption(s). This should be your first step for all of the Critical Reasoning question types. The conclusion and the evidence will be explicitly stated in the passage, while the assumptions will require you to sit and consider the author's point of view. What needs to be true in order for the conclusion to be correct based on the given evidence?
Consider the purpose of each sentence. Sometimes CR questions will ask what the function is of a part of the argument. You may see questions that ask "which role" a sentence plays. Try to place it into one category: conclusion ,or evidence? If the sentence was removed from the paragraph, what would be lacking?
Know the overall flow. Arguments have a tendency to follow one of two shapes: a triangle or an inverted triangle. Does the author start by making a specific conclusion and then provide more general evidence, or does he begin with observations and then get to a thesis? Use variables to describe the structure. "Y leads to X which leads to Z" is different from "Y turns into Z unless Y is prevented." Be on the lookout for "If X, then Y" relationship.
Paraphrase the argument. Dumb down the complexity of the argument as you read, as if you were explaining it to a child. You may want to write down a few short notes to help you. The idea is to ignore the petty details and see through to the author's main point and to the evidence he provides to support his point.
Choose a verb. Questions about argument structure often ask about the "methods" an author uses. You already know the flow of the overall argument, now give it an overall purpose and label as an infinitive verb. Common verbs:
to explain
to dismiss
to theorize
to strengthen
to demonstrate
to revise
to assert
to suggest
to interpret
to reconcile
to challenge
to predict
Look for transitions. Transition words and phrases are like signposts pointing your way through the logic of the argument. They tell you what is coming next. "Specifically..." means a more detailed example will follow. "Thus," means a summation is to be expected. "While this may be true..." is a phrase that shows a concession is about to be made. Keep a study sheet of transition words and divide them into categories: Examples, Adding, Contrasting, Emphasis, Resulting In, etc. It's an ongoing process to familiarize yourself with these, but a worthwhile one.
Determine what is missing for Complete the Passage Questions. What does the blank represent? Often it will be either a restatement of the conclusion, or another supporting piece of evidence, but it could also be an action advocating by the author, or an example of the author's argument applied to the real world.
Make a prediction (and write it down)! This is the most important strategy for CR. You've got to trust that you understand the argument enough to know what should be the correct answer. Don't worry about making it perfect - just get something down on paper! If you think of your prediction but don't write it down, you risk forgetting it or twisting it to fit the answer choices.
Eliminate out-of-scope answers. While the correct answer may not perfectly match your prediction, the simple fact that you took the time to think critically while you came up with a prediction will help you understand the author's focus and the flow of his argument. Eliminate answer choices that would NOT follow the gist of the paragraph. Especially look for those that are outside the scope of the author's focus, a favorite CR wrong answer type!
Good luck!
