Take-home and in-class exams are not the same animal. Let's face it, a take-home exam is essentially the same thing as a paper. So my best advice to you here is to treat it in the same way. That means:

• follow any instructions to the letter
• allow plenty of time to complete the exam
• proofread carefully before handing it in
  

An in-class exam, however, is another matter. Keep in mind that I am concerned only with in-class essays, not multiple choice tests. The suggestions here can be applied to any number of academic fields, as long as you're being asked to write an essay.

Some general suggestions first. You probably know all this, but it's advice worth repeating.

• Plan your studying schedule so that on the night before the exam, all you have to do is review briefly.
  
  
• Get enough sleep before the exam. No amount of cramming can make up for an exhausted brain.
  
  
• Wake up early enough to allow yourself time to prepare in a leisurely fashion. If it's a morning exam, eat breakfast! You need your blood sugar!
  
  
• When you're writing your exam, concentrate on how well you can write, not on how much you can write.
  
  
• Write clearly, leaving yourself room to make neat corrections. If you're writing your exam on a computer, double-space so you can skim your text quickly. Don't worry about mechanical errors as you write; leave them for the end, when you can edit your whole essay at once.
  
  
• Plan your time! Take 15 or 20 minutes to set up your thesis and outline. Then divide your remaining time to give yourself enough time to write, and then to edit and revise.

Yes, I did use the word "thesis." Your exam essay requires a thesis just like any other kind of essay. Write your thesis statement out in a place where you can refer to it frequently. It's the easiest and most effective way to prevent yourself from drifting off course.