Writing a good summary requires understanding the original text well enough to communicate the key points to others in a concise manner. A summary should be around 1/4 the length of the original and include the main idea, major points, and answers to basic questions of who, what, when, where, why and how, while ignoring unnecessary details. The process involves reading to comprehend the text, identifying important elements, drafting an objective summary using your own words and around the targeted length, and proofreading for errors.