Though you might be tempted to use Google to search for information you can use, there are better resources out there that will lead you to quality information (and leave out the chaff that often makes up half of the links in a Google results list). Try these resources:
Tips for searching library databases or indexes:
In-Text Citations
To cite sources in-text, use the last name of the author that provided the information you cited and the year of the publication. This information should appear in parentheses after the information or quote that you're citing.
Example:
The development of cooking helped Homo erectus derive more nutrients from food, allowing them to grow larger brains and eventually evolve into Homo sapiens (Brahic, 2010).
Exact quotations should include the page number as well.
Example:
According to Brahic (2010), "The key stumbling block for the theory that our early ancestors cooked their food is that as yet there is no convincing evidence that hominins could control fire more than a million years ago" (p. 12).
Bibliography Citations
Your bibliography (sometimes referred to as a "Works Cited" list) should consist of all the sources you cited throughout your poster. Journal articles you cite should follow this format:
Author'sLastName, Author'sFirstandMiddleInitials. (PublicationYear). Title of article. Journal in which article appears, Volume#(Issue#), FirstPage-LastPage. doi:http://dx.doi.org/xx.xx/yyyy.
Example:
Brahic, C. (2010). I cook, therefore I am...human. New Scientist, 207(2769): 12. (this is a one page article, that does not have a doi number)
For more examples of in-text and bibliography citations, consult this help guide.