Become familiar with the GRE issue essay pool of topics. This can be found online at the GRE Web site.
Take your time in selecting the topic on which to write. Make sure to pick the topic you feel strongest about and can most easily defend.
Write a brief outline of your paragraph topics before writing to help keep you focused. The GRE issue essay is timed so don't spend too much time on this step.
Write the main body of the GRE issue essay first. Save the introduction and conclusion for the last 15 or 20 minutes during revision time. This will allow you to review your main points for inclusion in the opening and closing paragraphs.
Use signal words as you write. Including words such as "furthermore" or "in contrast" will make the grader's job easier and reflect better on you as a writer.