Take careful notes throughout the listening section. For example, on the TOEFL, you will hear a short talk of around two minutes and then be asked to read a passage and combine the two pieces of information into an essay. If you don't take careful notes, it will be easy to forget where you learned which piece of information. Therefore, keep careful, organized notes about different speakers' opinions, the overall idea of the listening section, as well as details.
Especially for non-native speakers of English, large vocabulary words within a listening section can be intimidating and make it more difficult to later write a response to the listening. However, to succeed on a listening essay, ignoring those words and doing your best to write a cohesive essay without them will benefit you the most. The only exception to this is if a particular word, term or phrase is defined within the listening section, in which case you may be asked to address it later.
Depending on the purpose of your essay, it may require a different structure than other listening essays. However, a good model to begin with is the five-paragraph essay. This classic essay form has an introduction, a conclusion and three example (or body) paragraphs in between. Each paragraph should have a topic sentence that relates to your thesis statement and provide clear, vivid examples. If your essay is longer, add more body paragraphs; if it is shorter, remove some. However, the most successful essays will always have an introduction and conclusion, even if brief.
Even if your listening essay is timed, as it is on the TOEFL, always leave time to proofread at the end. The time you need will depend on your level of English and the length of the essay. It could be as short as five minutes on a timed essay or as long as several hours for a long take-home essay. When proofreading, look not only at the spelling and grammar, but also that you varied your sentence structure, used a good variety of vocabulary words and have considered other more global issues.