An introduction is the first paragraph of a written research paper. It has two parts:
1. A general introduction to the topic you will be discussing
2. Your Thesis Statement

Without an introduction it is sometimes very difficult for your audience to figure out what you are trying to say. There needs to be a thread of an idea that they will follow through your paper. The introduction gives the reader the beginning of the piece of thread so they can follow it.

Many books recommend writing your introduction last, after you finish your project. This is to make sure that you introduce what you are actually going to say. If your paper changes in the creating process, it is important to make sure that your introduction accurately reflects what you will be saying. If, however, you have written a good outline and stick to it, then it is fine to start writing your introduction first. Just make sure in your proofreading that you have kept the thread consistent throughout the paper.

Start with a couple of sentences that introduce your topic to your reader. You do not have to give too much detailed information; save that for the body of your paper. Make these sentences as interesting as you can. Through them, you can hook a reader and get them very interested in the line of thinking you are going to develop in your project.

Then state your thesis, which may be done in one or more sentences. The length of your introduction depends on the length and complexity of your project, but generally it should not exceed one page unless it is a very long project or a book. The average length of an introduction is one half a page.

Sample Introduction Paragraph
For the example, the regular text is the general introduction to the topic. The BOLD text is the writer's Thesis Statement.
Teenagers in many American cities have been involved in more gangs in the last five years than ever before. These gangs of teens have been committing a lot of violent crimes. The victims of these crimes are both gang members and people outside of gangs. Many people do not want to travel to areas in our cities because of the danger from this problem. For this terrible situation to stop, it is going to take a combined effort on the part of many people. Excellent, supervised after-school programs, more jobs available for teens, and healthy family relationships will go a long way towards ending this crisis in our society.

An introduction gives the reader an idea of where you are going in your project so they can follow along. You can give them more background details and supporting evidence for your thesis in the body of the paper itself.

Good Ways to Start Your Introduction Paragraph

Surprising fact: The pentagon has twice as many bathrooms as are necessary. The famous government building was constructed in the 1940s, when segregation laws required that separate bathrooms be installed for people of African descent. This building isn’t the only American icon that harkens back to this embarrassing and hurtful time in our history. Across the United States there are many examples of leftover laws and customs that reflect the racism that once permeated American society.
Humor: When my older brother substituted fresh eggs for our hard-boiled Easter eggs, he didn’t realize our father would take the first crack at hiding them. My brother’s holiday ended early that particular day in 1991, but the rest of the family enjoyed the warm April weather, outside on the lawn, until late into the evening. Perhaps it was the warmth of the day and the joy of eating Easter roast while Tommy contemplated his actions that make my memories of Easter so sweet. Whatever the true reason, the fact is that my favorite holiday of the year is Easter Sunday.
Quotation: Hillary Rodham Clinton once said that “There cannot be true democracy unless women's voices are heard.” In 2006, when Nancy Pelosi became the nation’s first female Speaker of the House, one woman’s voice rang out clear. With this development, democracy grew to its truest level ever in terms of women’s equality. The historical event also paved the way for Senator Clinton as she warmed her own vocal chords in preparation for a presidential race.
Finding the Hook
In each example, the first sentence draws the reader in to find out how the interesting fact leads to a point. You can use many methods to capture your reader’s interest.
Curiosity: A duck’s quack doesn’t echo. Some people might find a deep and mysterious meaning in this fact …
Definition: A homograph is a word with two or more pronunciations. Produce is one example …
Anecdote: Yesterday morning I watched as my older sister left for school with a bright white glob of toothpaste gleaming on her chin. I felt no regret at all until she stepped onto the bus
End With a Good Beginning
Once you complete a first draft of your paper, go back to re-construct your introductory paragraph. Be sure to check your thesis statement to make sure it still holds true—then double check your first sentence to give it some zing.