1. Think the topic over
First it is necessary to know what you are writing about. You should know and understand the topic, know all the pro&cons of the problem.
2. Structure of the essay
Think about the structure of your essay, about each part of it. What you are going to write about in the introduction - present the topic, the problem, in the body - conveniences, inconveniences and in the conclusion - your own opinion.
3. Start writing the essay
Don't forget to write in paragraphs. Keep your essay as simple as possible, the simpler your essay is the less mistakes you make.
4. Read it again
After finishing the essay, read it again and try to find the mistakes you have made. Check your spelling and grammar. If you are writing the essay with the help of computer, it can check the spelling instead of you.