Once you've spend five minutes (or less if you're really fast) brainstorming and you have some key ideas / keywords noted on a piece of paper, then you're ready to start writing. Your brainstorming notes will give you a good idea about the content of your essay. By looking at your ideas, you can understand quickly, for example:
do you have more advantages than disadvantages?
do you have more 'agree' ideas than 'disagree' ideas?
are your for and against ideas equally balanced?
Looking at your notes will help you to write your introduction. In your introduction, you want to write:
A general sentence about the overall essay topic (e.g. education, transport, health).
A more detailed sentence that refers to the specifics of the essay topic.
A statement of your intention or opinion.
So, for example, the essay topic statement is:
International tourism has brought enormous benefits to many places. At the same time, there is increasing concern about the impact on local inhabitants and their environment.
Do the disadvantages of international tourism outweigh the advantages?
My brainstorming has produced these ideas:
When I look at my ideas, I have more notes about the disadvantages of tourism, so I decide I will argue in my essay that there are more disadvantages than advantages.
Reading the essay topic statement again, I understand that:
The overall essay topic is tourism.
The specifics of the essay topic is benefits and disadvantages of tourism.
I need to write about whether the advantages are greater than the disadvantages.
These are the three things I need to cover in my introduction to ensure my introduction links to the essay topic statement. I also want to try and use some good vocabulary and, if possible, a range of grammar. So, I write:
The tourism industry has become a critical part of the economy of many countries, especially developing countries. However, there can be significant problems related to tourism. In this essay, I argue that the drawbacks of tourism are greater than the benefits.
My introduction is 40 words long and involves three sentences. Most importantly:
It clearly links to the essay topic statement.
It states clearly my intention and my opinion (which is based upon my brainstorming)
It uses some new vocabulary (highlighted in red)
It uses a range of grammar ('has become', 'can be', 'greater than')