Descriptive writing is familiar to most of us that read fiction regularly. It tends to be rich in adjectives and adverbs but for it to be done well requires a certain level of restraint in the use of such words. If you intend to write this type of paper about someone, here are things you should bear in mind to do it well.
These need not be about people. They may describe homes or beloved pets. What you are really trying to gain is a sense of how the writing should be done.
The people we know are naturally the easiest to describe. We will have seen their little habits and you know the way they speak. The better you know someone the easier it will be for you to write about them both convincingly and accurately.
If the essay you are writing focuses on someone you have not met, you do not benefit from first person knowledge in your descriptions. All is not lost as long as they have written their own story. This would show how they saw themselves and while they are likely to have an unrealistically positive opinion of themselves, this source is always useful.
Some people die without telling their own stories. You may have to look through someone elses’ version of events in that case. Some biographies are authorized by a person’s estate while others are unofficial. Whichever is available should be accessed and studied for whatever it can provide.
Much of what makes us who or what we are is not easily observed. We may have a distaste for sea food due to an overexposure to it in childhood or be exceptional musicians due to subtle parental influence. Some of these things require deep research into the place and time where an individual was born and raised. Do that research and you can take your writing to the next level.
You may be able to submit your work early and then do corrections as necessary to improve it. This advice is valid for all assignments if your teacher will allow it.
This is all that is required to write descriptively about someone as an essayist.