I just got asked about how to use the Economist for reading comprehension in another thread, and I have a lot to say on the subject so it's going here!
First off--The Economist is an amazing news source and it's often more interesting to get extra rc from them than from old tests.
The idea is to switch from passively reading the news to actively reading articles for the kind of stuff that the LSAT asks about.
It goes like this:
Read with a pencil/highlighter in hand and look for/underline the following:
1. The Main Point. In straight forward journalism and almost all RC passages, you can usually find the main point in the first paragraph. About 30% of RC questions deal with the main point, so getting good at finding it is important.
2. Stats, lists, definitions, dates--detail questions often deal with this kind of thing. It's good to learn to automatically make a note of this stuff so you can find it again easily.
3. The author's point of view as it's given away in adjectives and phrasing. The economist is great for this as most articles are editorial like--something is being argued but never too blatantly.
4. Competing perspectives--make note of when the critic or counter argument shows up.
Then, as you read, keep in mind the underlying logical structure of the passage. How is the case being made? Does it start with one historical argument and then challenge it? Are there dueling perspectives?
Keep the organization of the article in mind--you might even want to outline it for practice.
Basically, actively dissecting Economist articles for main point, argument, structure as you read teaches you to do these things automatically in RC. You'll anticipate questions better and get to the essence of the passage more easily. It's extra RC practice while keeping up on current affairs!
Here, try it: http://www.economist.com/daily/news/displaystory.cfm?story_id=10006840&top_story=1
Totally works as an RC passage, doesn't it?