Identifying Main Ideas
Before you start writing, it's a good idea to practice identifying main ideas as you read. A topic is the overarching idea or subject of a paper, but a main idea is a "key concept" within a paragraph. It is simply the focal point of that paragraph. If you're reading a textbook about mammals, mammals is the topic. Each paragraph should center on a main idea pertaining to mammals, such as their spinal functions or eating habits. All main ideas should relate to the overall topic of the paper.
Writing Main Ideas
When writing, make sure every paragraph of your paper clearly expresses a main idea at the beginning, and possibly again at the end. The first main idea is mandatory and gives your reader a clear idea of what that paragraph discusses. The main idea at the end is optional and can sum up the paragraph, provide a transition to the next paragraph, or both. For example, you may write a paragraph about aquatic mammals with a sentence at the end about how they compare to land mammals, because that comparison is the main idea of the next paragraph.
Identifying Thesis Statements
Every essay or research paper should have only one thesis statement. It is usually found near the end of the opening paragraph. This statement tells the reader the direction of the paper and how you plan to interpret the information. It can answer a question, make an argument or explain a problem. A thesis statement should be very specific and clearly capture the author's position on the topic; for example, "Aquatic mammals have more complex respiratory systems than land mammals." Now the reader knows that the author plans to present evidence to support this statement.
Writing Thesis Statements
You should always thoroughly research your topic and then think about it before writing a thesis statement. Pick one issue or aspect of your topic to focus on because thesis statements with multiple ideas are often weak and messy. You want to express a strong opinion that you can support with your research. For example, don't say, "In my opinion, aquatic mammals have more complicated respiratory systems." Just say, "Aquatic mammals have more complicated respiratory systems," then back up that statement throughout your paper.