The best way to prepare for an in-class essay is to understand how to use a basic outline.
All essays follow the same basic outline. If you really have no idea what the topic is going to be, this standard generic essay format is your best bet. You can therefore easily adapt whatever the topic is to this essay format.
The first thing you will want to do when you get the prompt is outline your essay. This will save you time in the long run, because you will get all of your ideas planned out and all that will be left is the writing.
In an in-class essay, the content is the most important thing. Teachers understand that this is a first-draft quality essay. There can be minor spelling and grammatical errors, and as long as the ideas are sound you will not lose much for them.
Deconstructing the prompt is key. This means reading it carefully. Annotate the prompt by underlining, circling, and numbering. Then you will not leave anything out.
The most important part of the essay is the thesis. Even if you do not include the standard introduction, you should have a thesis statement. This is one sentence that is going to answer the prompt in a clear, direct, and succinct (brief) way.
Craft your first sentence carefully. Instructors will not expect the deft touch of an essay that is assigned out-of-class, but it will be to your benefit to create a concise and interesting introductory sentence. (enotes)
Once you have written a clear sentence, the key is to support it. This is where planning with an outline comes in. You know that you are going to have three points supporting your thesis. Determine your points immediately and jot them down. You will be glad you did. Once you take the time to choose your supporting arguments before you write, you won’t leave anything out.
A major pitfall of the in-class essay is the propensity to ramble. For each point you discuss, support your assertion with examples from lectures, reading, or context in other ways. (enotes)
With careful planning when the essay starts, you will not need to know the prompt ahead of time. Make sure that you leave a few minutes to read your essay at the end. Re-read the prompt, and make sure you addressed everything.