The title may provide clues which will help you identify the main ideas which are covered. There may be clues words which suggest how the material is arranged. For example, words like "cause" "versus" suggest a kind of argument that the author may be making. "Kinds" or "types" often suggest definitions or lists.
2. Check to see if there are headings and subheadings in the text.
If there are headings and subheadings, the author may have already told you the main points. These headings and subheadings suggest the outline or structure of the article.
3. Check to see if there are italicized words or phrases in the text.
Usually an author puts words which are important or need emphasis in italics.
4. Find any lists of points that are set off with numbers or paragraphs that begin with "first," "second," and so forth.
These points may be the most important part of the selection.
5. Sometimes the same idea is repeated.
If an idea is repeated in a different form, the author may be trying to reinforce the main or important idea.
6. Read the first and last paragraph of the selection.
Because main ideas are generalizations, the author may begin and end with a statement which generalizes or summarizes the ideas.
7. Read the first or last sentence of each paragraph if the main ideas are still unclear.
Often the author states the main idea in what is called a "topic sentence "at the beginning of the paragraph, although the sentence is sometimes found at the end or in the middle of the paragraph. Sometimes there are paragraphs with no topic sentence. In those cases, you must read the entire paragraph.
http://www.eduref.org/Virtual/Lessons/Language_Arts/Reading/RDG0200.html