the topic sentence states the main idea of the paragraph. There are many ways in whice one can do this. Some possible techniques include: definition, a nalysia, statistics,comparison and cause and effect.
The topic sentence needs to be the most general sentence of the paragraph.Meaning that it doesn't need to have too much detail or too much "fluff". The following sentence will then expand on the topic sentence.However,one dose need to establish the point of the paragraph so that reader can get a good idea of what the paragraph will include,just from the topic sentence.