Distinguishing general and specific ideas. In the first place you need to understand that some words or sentences are more general or inclusive than others. Thus, being able to differentiate specific from general information is essential because it will help you to be able to determine the main idea of the passage.
Now read the following list of sentences and find the sentences that gives the general idea of the others.
a. Some of the most common storms are rain storms,ice storms,blizzards, and snow storms.
b. A hurricane is another kind of storm that is known for its strong winds.
c. There are many kinds of storms.
d. Another type of wind storm is called a typhoon.
You should find that the third sentence gives more general idea than the others, thus it is the main idea of this set of sentences.