I consistently have the most trouble on Critical Reading questions that ask me to make inferences about the author's point of view in the passage. What's the best way to improve my performance on these types of questions?
The best way to improve on inference questions is to always look for direct evidence in the passage to support your answer, even if the question seems subjective. Use process of elimination to get rid of all choices that are not supported by information in the passage. Try to do as many relevant practice questions as you can to strengthen your skills.
You might also consider getting a review book to help guide you through these questions; I recommend The Critical Reader by Erica Melzer. If you don't want to buy a book, this article is a good place to start for some strategies that will help you through these types of questions: http://blog.prepscholar.com/inference-questions-on-sat-reading-6-strategies.