There are a number of different types of annotation you may do while reading an essay. Underline the thesis statement and topic statements, making notes in the margin identifying each as such. Circle or highlight text, then use an abbreviation to note in the margin what kind of text it is. Write notes in the margins in which you pose questions, express opinions disagreeing or agreeing with the text, make notes to do further research on a topic or relate what you are reading to something else, such as a personal experience, another essay or a documentary. You might also note the different kinds of rhetorical devices the essayist used and note how you might use similar devices in your writing.
Annotating an essay helps you break it down into manageable parts and think about how they all work together to accomplish the author's goal. This way you can more easily understand and think about the difficult philosophical, scientific and aesthetic concepts presented in college essays. Relating what you read to your personal experiences helps you anchor something unfamiliar with something familiar, improving the chances of understanding it. By breaking apart an author's argument, you can also better understand logic, rhetorical strategies and how to use evidence to back up your arguments.
By annotating you can practice connecting what you read with other texts and your opinions. If you read several essays in preparation for an in-class discussion you can make notes in the margins of each to compare and contrast those essays. This helps you better understand how experts can oppose and support each other through academic discourse and how you might add their own opinion to this conversation. This also helps you as you attempt to develop positions on controversial topics in order to write argumentative essays.
By annotating the essays you read, you may more easily re-enter those essays when you must write about or discuss them. Annotations may help you remember where you found a quote helpful for papers or questions on a subject you want to raise during class discussion. Armed with an annotated essay, you can quickly respond with counter arguments or further support when students begin to debate an issue during class. Students planning to enter graduate study can keep their annotated essays for years so that they can always find, with relative ease, their responses to arguments or pieces of evidence they find particularly beneficial to their area of study.