Here’s the approach I used with my son.
Day 1. Sit down with a list of the Common App prompts, each on a different page. Set a timer for 4 minutes per prompt, and brainstorm anything you could possibly consider using-- no idea is too off the wall at this stage.
Twenty eight minutes later, you’re done for the day.
Day 2: Go through your lists and either bullet what you could say about each topic or eliminate it. This could take a few days worth of 30 minute sessions, depending on the length of your original lists. At the end, you’ll probably have 6-10 possible essays.
Day 3. Detail what you’re planning to say for each topics. Bullets are still fine. No worries about intro or conclusion yet.
Day 4. Read through what you have. Eliminate any that don’t really address the prompt. Eliminate ones that are cliché (like how you learned through failure after not making the freshman basketball team, then went on to make Varsity as a junior.) Eliminate those that concentrate on a failure as opposed to growth. Eliminate those in which you’re a passive bystander. (After Hurricane Sandy, we lost power for 10 days. It was hard. But I learned to be tough.) Keep only those that “give them a reason to say yes.”
Day 5: Start writing the body for the topics that remain.
DAy 6. Decide which you like best, and begin editing.