段的基本组成是句子，好的段落应该是该段中所有的句子都围绕着一个主题展开，且句与句之间应该是紧密相连，形成统一的整体即unified and coherent。那么怎样将一个段落展开呢？下面介绍英语中几种常用的方法。
My heart gave a leap when I heard the announcement that our train would soon arrive at its destination-Beijing. Like other passengers, I began to collect my things and put my mug, towel, atlas, apples, and other things into my bag. To the tune of a beautiful song the train pulled into the station and gently stopped by a platform. I walked out of the train and was carried forward by the stream of people into an underground passage and then into a big hall. As I stepped out of the station, I was dazzled by the bright autumn skies of Beijing. Though I had been on the train for more the thirty hours and spent an sleepless night, I didn't feel tired at all, and I believed my days in this glorious city would be as sunny as the skies.
In the middle of the rectangular-shaped courtyard stood three magnolia trees(), all in full bloom. A little girl was hoping among them, now gazing at a bud, now collecting fallen petals. Under one of the trees stood her parents, who, while keeping an eye on her, were examining the snow white blossoms with great interest and admiration. In front of another tree a young couple, fresh and bright as the flowers, were posing for a picture. At the end of the courtyard a group of youngsters had gathered behind an artist painting a flourishing limb, which looked so charming and real that a boy stooped to sniff at a half-open flower. At the opposite end a few elderly men and women stood admiring the leafless flowering trees and the people looking at them.
(3)列举法 通过列举一系列的论据 对主题句中的论点进行广泛、全面的陈述或解释，列举的顺序可按照所列各点的内容的相对重要性、时间、空间来排列，例如：
The Other Side of City Life
In the eyes of many people, city life is attractive with all its advantages and convenience, yet they don't see the other side of the picture. First, with the expansion of the city, housing has become a serious problem for city people. Then, there is the problem of pollution: harmful gases from vehicles and poisonous water from factories pollute our surroundings; noise continually disturbs your peace and rest and drives you mad. Thirdly, modern city life puts a high pressure upon people; you have to hurry to and from work; you have to dodge in so as to avoid bumping into the flood of people, bicycles, cars, buses…; all day long you are under great stress. Fourthly, big cities also cause some social problems. Of which high crime rate is the most serious one. People are justifiably in fear of becoming victims of burglary, robbery, murder and other crimes at any time. They should find some ways to cope with all these problems.
This term several useful and interesting courses have been offered. An Introduction to European Culture, for instance, gives us a lot of background knowledge of the history of European philosophy, literature, and arts. From time to time we see slide shows of famous paintings and hear tapes of famous pieces of music, and they make the lectures all the more interesting. American Society and Culture is another course that attracts a large audience. The teacher, who visited the United States not long ago, discusses new trends and changes in American life as well as American history and traditions. We like these and other courses very much, because they help us not only to improve our English but also to broaden our vision.
比较和对比常有两种形式，即整体比较和对比(block comparison and contrast)与逐项比较(alternating comparison)，例如：
Although Ulysses S. Grant and Robert E. Lee were fierce adversaries during the Civil War, their lives, both military and nonmilitary, has a great deal in common. Grant descended from a family whose members participated in the American Revolution. He received his commission of second lieutenant from West Point and served in the Spanish-American War. He was later summoned by President Lincoln to assume command of the Union Forces during the Civil War. After the Civil War, Grant suffered financial problems and was forced to declare bankruptcy. Lee also descended from a family which engaged in the American Revolution. He, too, received his commission from West Point and later fought in Mexico during the Spanish-American War. His fame as a military strategist during the Civil War, when he was the commander of the Confederate armies, is well known. Although it is not always pointed out by historians he, like Grant, had financial difficulties after the civil War and was compelled to declare bankruptcy. By securing a post as president of Washington College, he was able to avoid additional poverty.(整体比较)
The same qualities that make people good houseguests make them good hospital patients. Good houseguests can expect a reasonable amount of service and effort on their behalf, and hospital patients can also. Guests have to adjust to what is for them a change, and certainly hospital patients must do the same. No one appreciates a complaining, unpleasant, unappreciative house guest, and the hospital staff is no exception. Hose guests who expect vast changes to be made for their benefit are not popular for long. Certainly nurses and other personnel with their routines feel the same way about patients in their care. Just as house guests must make adjustments to enjoy their visits, so patients must make adjustments to make their stays reasonably pleasant and satisfying under the circumstances.(逐项比较)
The surge of demand for oil will soon begin to send shock waves through the American economy and transportation system. The impact of these tremors can already be anticipated: to the consumer they signal the end of a long love affair with the car, and to Detroit they offer an early warning that its 1985 growth aims are dangerously unrealistic. Unless we exercise foresight and devise growth-limits policies for the auto industry, events will thrust us into a crisis that will lead to a substantial erosion of domestic oil supply as well as the independence it provides us with, and a level of petroleum imports that could cost as much as $20 to $30 billion per year. Moreover, we would still be depleting our remaining oil reserves at an unacceptable rate, and scrambling for petroleum substitutes, with enormous potential damage to the environment.
(7)定义法 有时候为了避免混淆或误解，我们必须对一个词、一条术语或谚语、一个概念通过下定义加以说明、解释。通常有三种方法下定定义：给出同义词、用一个带有定语从句的复合句或用一整段文章，而以第三种方法最为常用。1997年1月份四级考试的作文Practice Makes Perfect就是一篇极为典型的定义型文章。再看下面的例子：
A "liberated woman" is simply a woman who controls her own life, rather than allowing it to be controlled by other people, traditions, or expectations. A "liberated woman" can be found pursuing any line of work, including housework, or no work at all. She may or may not be married; she may or may not have born children. She may belong to any race; she may have attained any age. She need have only one trait in common with her "liberated sisters": she makes her own choices, whether they be the colors on her walls or the advanced degrees she seeks. She acts of her own volition, responsible to herself, and not out of fear of what her mother, lover, or neighbor might say.
According to Xiao Li, the fifteen students of his class fall into three groups. Seven of them work hard and study well. They always get good marks in examinations and are often praised by the teachers. Li calls them "good students". The monitor, the secretary of the Youth League branch, and the captain of the class volleyball team, are quick in finding out what their fellow students are interested in or what they should do as a collective. They always organize proper activities at the proper time, so Li calls them "good organizers". Four other students are very kind to their classmates, always ready to lend them a helping hand. They help to clean the classroom and the corridor even when they are not on duty. Li says that they are "good fellows". "What about yourself?" someone asks him. "I'm a group by myself-a good observer."
先说记叙文。所谓narration就是叙述一件事或一连串事件，像四级曾经考过的A Morning Walk(晨间漫步)即是一例。在写这类作文时，要注意以下几点：首先，在一开始就要设定时间、地点、人物，一定要交代清楚；其次，在讲述发生的事件本身时，要选取一些关键的细节，不要漫无边际或不着边际，而组织那些素材一般采用"时间顺序"亦即先发生的先写，后发生的后写，或用倒叙法，先讲结局，再从头描述经过。另外，要注意人称、时代的一致性。
再谈谈说明文。这是四级考试中出现最为频繁的体裁，无论是A or B、A and B，还是Why to do、How to do, 或是图表型作文，都可归入此类。如果说描述文主要涉及外表和感受，记叙文主要涉及事件和经历，那么说明文则主要是关于过程和关系。举例来说吧，我们面前有一件物体，如果要对其外观进行描写，我们就要写成描述型的作文，如果要解释它是如何制作的，又是如何使用的，那就必须写成说明文；我们可以讲述一个历史事件，到底发生了什么，何时何地发生，都有谁参与其中，那就是叙述，而要讨论该事件的前因后果，它的本质又是什么，以及在历史长河中的深远意义，那就必须写成说明文。前面所介绍的展开段落的方法，如分类法、定义法、比较和对比、举例法等等，大多数都可用于说明文的写作。