The big idea
You cite your sources to prove to your reader where you got your information. In some instances, the reader may be so interested in what you wrote that he or she wants to read more about the topic. Citations tell where to find the same sources you used.
Before you begin
Be sure that you keep track of all necessary information AS YOU ARE DOING YOUR RESEARCH. Jot down the title of the book or magazine, author, publisher, date, and so on. Writing this stuff down as you go is one heck of a lot easier than going back to the library later on to hunt it all up.
How to do it
Parenthetical references are one way to show where you got your information for a research paper. Parenthetical references are not the same as a bibliography. Not, not, not.
The parenthetical references generally have a couple of words, like "(Kirk 100)." The first word is the last name of an author. You can find the rest of his name, and the name of his book, in the bibliography, alphabetized under "K" for "Kirk." The second word--number, actually--is the page number in that book where the fact came from.
Some sources don't have an author. Then just use the first word or two of the title, like "(Flob)" or "('Other People's')."
Sometimes, as with web pages, there is no page number, or like with an encyclopedia article, the page number doesn't matter. In that case, just skip the whole page number thing.
What to cite:
Where to cite
At the end of each sentence. Here's what it looks like. Look for the information in parentheses at the end of certain sentences. Those references tell you where to look on the bibliography page to learn where each fact came from. I've made them red here so they stand out, but don't do that in your own papers.
Notice also that the parenthetical reference comes after the quotation marks (if there are any), but inside the period at the end of the sentence.
. . . .
An example
The sport of twenty-meter freestyle skunk kicking was invented by Bob Flob on March 25, 1957. Flob was angry at a skunk which had been chasing him as he rode his bike. "Leaping off his bicycle, Flob picked up the skunk, dropped it, and booted it through the air. Yowling in pain and fear, the skunk sailed cleanly between two telephone poles. A new sport was born" (Smith 43). Since that day, skunk kicking has grown in popularity, and is now played in 93 countries (O'Williams). It was introduced as an Olympic sport in the summer games of 1992 in Barcelona, and a winter variation, skunk hockey, will make its appearance in the winter games of 2006 (Kirk 100). It has even been featured in a number of motion pictures, even though the blockbuster movie Flob changed some of the facts to make the story more interesting (Flob). Clearly, the sport has become an important part of societies the world over, in ways that nobody could have imagined on the day that Flob abused his first polecat ("Other People's..."). Of course, the sport has changed since Flob's day: the modern skunk-kicker uses an impressive array of safety equipment and the skunk can be either punted or kicked off a tee.