TOEFL iBT Independent Writing Structure.
The objective of the TOEFL independent writing essay is to assess your ability to clearly and logically express your ideas in English. To do this well you not only need to be able to write English at the sentence and paragraph level but also at the essay level. A TOEFL independent writing essay should be at least four paragraphs long (five is probably better, but six is probably too many). These 4 or 5 paragraphs should be divided into an introduction, a body, and a conclusion.The basic structure of a TOEFL independent writing essay should look like this -
Introduction
Body Paragraph 1
Body Paragraph 2
Body Paragraph 3
Conclusion

Let's look at what we need in each of these different parts of the essay.
Introduction
In the introduction we need three things: background information, hints at essay development, thesis statement.
1. Background information is some kind of general statement about the topic of the essay. It does not actually answer the question posed in the essay topic, but gives the reader the impression that you (the writer) know about the topic, have thought about the topic or have experience of the topic.
For example, if you are asked to write an essay on the topic 'Which do you prefer, tea or coffee?', your background information might be something like "Tea and coffee are two of the most popular drinks in the world. Most people on earth probably drink one of these beverages at least once every day: I certainly do."
2.The hints at essay development should give the reader some idea of what you are going to talk about in your essay. DO NOT say things like 'I have three reasons', or 'there are two reasons for this' in your introduction. The hints at essay development will tell me your reasons. For example, if you are asked to write an essay on the topic 'Which do you prefer, tea or coffee?' and you write, "Tea is healthier, tastier and cheaper than coffee." , that would be your hints at essay development.
3. The thesis statement is your position on the topic. For example, if you are asked to write an essay on the topic 'Which do you prefer, tea or coffee?' and you choose to say, "I prefer tea", that is your thesis statement.

The standard order in an Introduction is -
1.background information
2.hints at essay development
3.thesis statement
although
1.background information
3.thesis statement
2.hints at essay development
is also possible and often easier to write.  Let's see how they go together using the examples above. First using 1,2,3 order.
Tea and coffee are two of the most popular drinks in the world. Most people on earth probably drink one of these beverages at least once every day: I certainly do. Although I like both of these drinks, I feel that tea is tastier than coffee, and not only cheaper, but also healthier. There is no question in my mind that I prefer tea.
Now using 1,3,2 order.
Tea and coffee are two of the most popular drinks in the world. Most people on earth probably drink one of these beverages at least once every day: I certainly do.  However, there is no question in my mind that I prefer tea. For me, tea is tastier than coffee, and not only cheaper, but also healthier.
Body Paragraph 1
In each body paragraph we explain or discuss one of the hints at essay development that we mentioned in the introduction. This becomes the topic of the paragraph. What we actually need in each body paragraph is -
Topic sentence (this tells the reader what the paragraph is about)
Supporting sentences (these support and explain what is stated in the topic sentence)
For example, using one of the hints at essay development mentioned above, you might write a topic sentence like "Firstly, tea is generally regarded as being much better for our health than coffee." , Next you would write some supporting sentences that make the reader realise that what you said in your topic sentence  is correct. For example
"For thousands of years the Chinese were sure of the positive effects of tea on our health and modern scientific research seems to support these ancient beliefs. Tea is now known to help prevent certain types of cancer. In addition it seems tea can help lower both stress and cholesterol levels in our body. At a  less serious level tea, unlike coffee, is rarely drunk with milk and sugar and therefore contains fewer calories than a comparable cup of coffee. All in all it is a much healthier drink."
Body Paragraph 2
The same structure as Body Paragraph 1
Secondly, the taste of tea is much more pleasant that that of coffee. It is true that there are many, many flavours of tea, but almost always the taste is mild and smooth. Coffee has a bitter taste that for many people needs to be sweetened by sugar. This bitterness gives coffee a strong, very distinct taste.With tea the taste is much more delicate and I prefer the subtlety of taste which it offers.
Body Paragraph 3
The same structure as Body Paragraph 1
Finally, although  probably  most importantly, tea is not nearly as expensive as  coffee. As a poor university student this is a major consideration for me. At the supermarket, a  one-litre bottle of coffee costs almost as much as a two-litre bottle of tea. That is a very large difference. Furthermore, when we consider the price of a pack of loose tea leaves to a bag of ground coffee, the difference in price is even greater. Probably the largest difference in price is between tea bags and similar filter-coffee bags, where tea is approximately five times cheaper.
Conclusion
In the conclusion we need to tie everything together by summarizing the main points of the essay again. We can most easily do this by restatement. When we do this we are basically repeating the hints at essay development and thesis statement that we wrote in the introduction. Be very careful that you do not just copy the same words. You MUST restate them - that is use different words. For example, in the introduction I said 'tea is healthier', in the topic sentence of body paragraph 1, I said 'tea is better for our health' and in the conclusion I might say 'tea is better for our bodies'.
 
Let's look at the completed essay without the explanation.
Introduction

Tea and coffee are two of the most popular drinks in the world. Most people on earth probably drink one of these beverages at least once every day: I certainly do. Although I like both of these drinks, I feel that tea is tastier than coffee, and not only cheaper, but also healthier. There is no question in my mind that I prefer tea.

Body Paragraph 1

Firstly, tea is generally regarded as being much better for our health than coffee. For thousands of years the Chinese were sure of the positive effects of tea on our health and modern scientific research seems to support these ancient beliefs. Tea is now known to help prevent certain types of cancer. In addition it seems tea can help lower both stress and cholesterol levels in our body. At a  less serious level tea, unlike coffee, is rarely drunk with milk and sugar and therefore contains fewer calories than a comparable cup of coffee. All in all it is a much healthier drink.

Body Paragraph 2

Secondly, the taste of tea is much more pleasant that that of coffee. It is true that there are many, many flavours of tea, but almost always the taste is mild and smooth. Coffee has a bitter taste that for many people needs to be sweetened by sugar. This bitterness gives coffee a strong, very distinct taste.With tea the taste is much more delicate and I prefer the subtlety of taste which it offers.

Body Paragraph 3

Finally, although  probably  most importantly, tea is not nearly as expensive as  coffee. As a poor university student this is a major consideration for me. At the supermarket, a  one-litre bottle of coffee costs almost as much as a two-litre bottle of tea. That is a very large difference. Furthermore, when we consider the price of a pack of loose tea leaves to a bag of ground coffee, the difference in price is even greater. Probably the largest difference in price is between tea bags and similar filter-coffee bags, where tea is approximately five tmes cheaper.

Conclusion
In conclusion, the fact that tea is better for our bodies, is more acceptable to my  tastebuds, and does not impoverish me when I buy it, makes the question of which drink I prefer an easy one to answer. Even though I often drink both tea and coffee, if I ever had to choose to drink only one for the rest of my life, I would have no hesitation in selecting tea. (409 words)

Important Points
1) When we move from one paragraph to the next we need to make a smooth transition the the next paragraph. The easiest way to do this is to use words such as First, Secondly, Finally and In conclusion. There are many transition words, but these are the easiest?
Can you think of any other words or phrases you could use to move from paragraph to the next in the essay above?
2) Try to use different words when you change your hints at essay development into topic sentences, and then again when you restate in the conclusion. You need to think about synonyms.
Can you see any  synonyms in the essay above?
3) You need linking words to hold your essay together.
Look at the words 'in addition' in body paragraph 1. They tell the reader that you are moving on to another point.
Can you see any other linking words?