命題作文要求就所給的作文題目進行寫作。與其他作文相比，命題作文具有較大的自主性。因爲同樣的一個題目可以從不同的角度、用不同的文體來進行寫作。例如“My Teacher”這個題目可以寫成一篇記敘文，也可以寫成一篇描寫文。不管用什麼文體，也不管從哪個方面來寫，只要寫出的`文章切題、流暢、條理清楚、語言正確就是一篇好文章。然而，這種較大的自主性也會使考生感到困難。因爲在有限的30分鐘之內，要形成提綱，並寫成短文並不是件易事。這就要求考生在寫命題作文時首先一定要審好題，要仔細分析題意，搞清楚題目所涉及的範圍，確定文章的中心思想，切忌跑題。再者，要選擇正確的文體。最後，要圍繞文章的中心思想，將寫作素材進行分析、歸類並寫好寫作提綱，包括：引言句、主題句和結尾句。
［例1］Fake Commodities
Markets all over the country are swamped with fake and poor commodities. This has harmed greatly the state餾 interests and people餾 health. For example, false poison made in a factory not only can餿 kill mice, but also gives them immunity and makes them healthier.
The cause of this serious situation is that some enterprises only want to get benefit. What餾 more,some local governments, for the purpose of local protection, don餿 investigate such activities,on the contrary, they even support them. The judicial organs don餿 punish the offenders strictly.
We hold that the whole society should pay greater attention to these illegal activities, and these illegal activities should be punished according to the law. The leaders in charge should take effective measures to stop these harmful activities. Consumers should learn to protect their own interests, and not to buy fake commodities. In this way, we can at last wipe out fake commodities and leave no room for them.
作者把這個題目寫成了一篇說明文。一開始先指出了假冒僞劣產品的危害。接下來分析了這一情況產生的原因，最後呼籲全社會都來關注這個問題。
［例2］Haste Makes Waste
There is an old Chinese saying,“Haste makes waste.”It was true in the past, and it is still true in many cases today.
Usually, if you act faster, you can reach your goals earlier. But it isn餿 always the case. If you emphasize only on speed but ignore the quality of your work, you will get the opposite result. Suppose you are preparing for your final examination. You have so many things to do that you don餿 have enough rest. You have to read and write continuously. The result is that your brain is less and less efficient, and the situation goes from bad to worse. All your efforts become fruitless. On the contrary, if your preparation follows a carefully worked out plan，your work will be effective. Consequently you will take part in the examination confidently.
Whatever you do, please remember the saying—Haste makes waste. If you can properly understand its meaning, you’ll benefit a lot from it.
作者在文章的開頭透過重複作文的題目巧妙地點了題，接下來用具體的事例來說明這一衆所周知的道理。