Purchase preparation tools for the TOEFL exam from ETS, the body that runs and administers the tests. If your budget is tight, you can download some free sample questions from the ETS website.
Read a range of typical essay questions and sample essays. The book "Barron's How to Prepare for the Computer-based TOEFL Essay" contains many such samples. Study the structure of the essays and the language used.
Brush up on your essay-planning skills at least two months before you are due to take the test. Practice planning an essay for five to ten minutes; use a variety of techniques to find out which one suits you best. Try quickly making a list of points you'd like to address; if the essay asks for advantages and disadvantages, divide your paper into two columns. Another technique is to use a mind map, placing the essay topic in a circle in the middle of the page. Draw thick lines out from the center and write your main keywords for the essay. Planning will speed up your essay writing.
Hone your skills at essay writing. Structure the essay into four paragraphs, suggests English for Students. Write an introduction that sets out your argument and follow up with two paragraphs that explain and expand the argument. The last paragraph should sum up your article.
Keep your sentences tight and short. Avoid clauses unless you are fully confident about your language skills. Likewise, avoid words if you are unsure how to spell them or if you do not really know what they mean.
Revise each essay that you complete. Check for punctuation and spelling and make sure the essay makes sense and that it answers the question.
Time yourself for each practice essay. Choose a real essay question and set a timer for 30 minutes to write an essay supporting your argument. The time should include time for planning and revision.
Set up a group practice session if you know other people who are preparing for the TOEFL test. You can all write on the same topic at the same time and then "score" one another's essays.