This introduces the main idea of your essay and draws the reader into the subject. A good introduction gets to the heart of the subject and captures the interest of the reader. It should:
Most students write poor introductions that needlessly repeat information and turn off the reader with too much background information. If you want to gain a top grade for your essay, you have to start strongly and gain your reader's attention immediately. This means concentrating on either writing a powerful summary of the essay or directly answering the question set.
In trying to gain the reader's attention, you do not need to say anything controversial or mind-blowing. All you need to do is concentrate on writing the most relevant information.
Too often, students write a warm-up first paragraph. Phrases such as: The purpose of the essay is to examine the various contributory factors leading to... or In this essay I shall examine the methodology used to assess... usually give little information. Such phrases could introduce any essay and do not present any information. For example:
Weak opening paragraph
The purpose of this essay is to examine the effect of Einstein's theories in the historical context of accepted propositions and laws of motion and the effect these theories had on current thinking in the field of physics. In so doing, the author will show that despite opposition to Einstein's theories when first published, these were indeed special works that reshaped current thinking to replace the ideas propounded by Galileo and Newton.
Stronger opening paragraph
Einstein's Theory of Special Relativity and Theory of General Relativity reshaped the world of physics by contradicting the existing laws of motion proposed by Galileo and developed by Newton. Although Einstein faced great opposition when proposing his theories, his work reshaped the thinking of future generations of physicists.
Use the journalistic technique of basing your information around the Five-Ws in writing: Who, What, When, Where and Why. These will help you keep to solid information.
Remember, don't use your introduction as a warm-up - make it direct, relevant and impressive so it sets the tone for the rest of the essay.