Well, since you're a non-native, the root of the problem might be your overall practice with English in general. Do you use English on a daily basis? Do you often come across well-written passages? You'd be surprised at how much your skills improve once you really start using the language, i.e. every day for 30 mins - an hour.
There are two reasons why reading stuff will help:
- you read faster
- your vocabulary will improve, which means you'll be able to better understand passages
There's not much to be said about RC other than that. But here's what I responded to a message asking me about some tips:
What you need to remember is that RC passages are usually well-written. This is the reason why they have a particularly clear structure, i.e. first paragraph - introduction; second paragraph - alternate explanation to a theory etc.... The paragraphs are linked to one another in a neat way, meaning that there's usually no abrupt "rupture" in the text. You will often see connectors, such as therefore, however, moreover to signal that a different section is about to come your way - like an alternate explanation (for however) or something that strengthens the initial idea (for moreover).
I usually follow the structure of the passage by these red flags, so to speak, which enables me to understand the purpose each paragraph in the whole thing. This is another important part of RC: you must be able to spot the purpose of each paragraph. That's particularly useful when you have questions such as "What is the main point of paragraph X?".
While this is the "macro" level of the stimulus, the "micro" level concerns each phrase of each paragraph: they too are connected by similar words. Each phrase has its own little role in everything! You should look for parallelisms, enumerations, supporting ideas: this gives you a general feel for it all.
Also, an important part of your RC practice is trying to work on your vocabulary. Most of the times, the answer choices that just take whole groups of words out of the text are wrong - this is a "cheap shot" designed to test you attention. The right answer will not only test your understanding of the passage, but it will also check for the "strength" of your vocabulary, your rephrasing "capabilities".
To sum it all up: read the passage critically, just as you would if you were an established book critic! Look for the "signs" and avoid traps.
