Skimming is a reading technique wherein one tries to find the main ideas of a reading material in order to know what it's generally about. It helps save time because there's no need to remember specific details. It's all about the gist of the selection.
In skimming materials, often you will find the main ideas in topic sentenceswhich are usually found in the first or last sentence of each paragraph. I say'usually' because there are also times when the topic sentence can be located in the middle of the paragraph, and at times there's no topic sentence at all. In this case, the main idea is implied. If it's a very long selection, you can just usually read the first paragraph and/or the last paragraph, for the first paragraph introduces the topic and the last paragraph often summarizes all the ideas presented in the material.
Can you find the topic sentence in the paragraph below?
Jake has a lot of great qualities that make girls fall for him easily. He is hardworking. He's also very intelligent. He is kind and can be considered a true gentleman. Furthermore, he is thoughtful and generous. Above all, he is undeniably good-looking.
Answer: first sentence
How about the paragraph below?
The sky is very dark today. It hasn't stopped raining since early this morning. Very few people are on the street and children cannot play outside. It's a very gloomy day.
Answer: last sentence
Can you guess the main idea of the paragraph below?
Some women are fashionable. Some are very smart. There are also women who are stronger than men. Some women are workaholics while some are just concerned about how to stay pretty.
Answer: There are many types of women. There's no topic sentence in the paragraph though. The main idea is implied.