There are many ways to write. What you write depends on WHY and to WHOM you are writing. Before you start your writing, you need to ask yourself these simple questions.
Why am I writing?
Who am I writing to/for?
What am I writing?
What should my writing contain?
How should my writing be organised?
Are there ceratin ways of doing that type of writing?
For example if you are doing an IELTS General Writing Task 1 consider these summary points to the questions above -:
Why are you writing? - maybe to complain about something, respond to a friend, apply for a job etc...
What are you writing? - a letter
To/ for whom are you writing? - maybe your university tutor, a friend, officer etc...
How will you write it? - you will write the letter in semi-formal language either explaining the problem, asking them to take action, offering help