我们在写主题句作文时应按下列步骤进行写作：
1. 仔细阅读指令，明确写作题目及其它要求。
2. 仔细推敲主题句。
主题句是段落的主导思想，是作者要加以说明，论证或描写的中心。因此在做主题句作文时，一定要仔细推敲找出所要阐述、说明或论证的重点，然后围绕主题句展开想象，进行论证、说明或描述。有些考生见到文章的主题句后，不善于分析，而是马上动笔写，结果写出的文章语无伦次，不深不透。还有的考生则是看过第一段的主题句后便顺势写下去，结果把三段的内容写在一段里，这都是不可取的。
3. 找出支配全段的主导思想。
分析主题句要找出支配全段的主导思想。支配思想对全段起统帅作用，并决定全段的发展方向。如以上三段各主题句中的支配思想分别为“more and more important part”，“more and more serious”，和“solve this problem”。
4. 选材和拟定提纲。
准确、全面地理解了文章的主题后就可以根据主题句确定要写的基本内容以及表现这一内容的材料，并拟定写作提纲。选材时，要准备分别用二、三个事实对主题加以论述，说明或描述。
5. 段落写作。
主题句只是提出了一段的写作中心，要进一步表达思想，就要展开段落。考生在进行段落写作时应注意段落的统一性和连贯性。段落的统一性（也说单一性）是指每段应只有一个中心思想，段落中所有的句子都围绕中心思想进行发挥。段落的连贯性是指段落的每一个句子都应按一定的逻辑顺序排列，句与句之间的过渡必须自然，转换必须顺势，衔接必须紧凑。
参考范文：
TV and Education
TV is playing a more and more important part in education today. Millions of people in China are learning foreign languages through TV. Adults watch TV every day for a great variety of courses. Special English-learning programs are available on TV for preschool children. TV is now quite indispensable in education today.
But the problems with TV today are also growing more and more serious. For example, school children keep watching TV until late at night, leaving little time for school assignment. Watching TV for so many hours a day certainly spoils their eyesight, and makes them less enthusiastic in school studies. What is even worse, so many telefilms and teleplays are about love affairs that a great number of students begin to make friends of the opposite sex or fall in love at a much earlier age than before.
Some suggestions have been put forward in attempt to solve this problem. Parents ought to help children select appropriate TV programs and set up some time limitations. School teachers ought to tell students how to make correct use of TV programs. TV stations should be careful in the selection of movies and plays. Newspapers and
journals
