The purpose of a proposal is to clearly define a plan of research and to place your proposed approach in context with what has been done. It should provide enough detail so that someone with skills similar to yours could take the proposal and do the project. In essence, if I were to replicate you at this moment and put your ``clone'' in a sensory deprivation chamber until the due date of the proposal, then I should be able to give your proposal to the clone and expect that it could carry the project to completion.
A proposal for an experimental study might include the following sections:
You should pick a convention for citing material. I honestly don't care which one you pick as long as it is not of your own making and you use it consistently and correctly. The Chicago Manual of Style and the Publication Manual of the American Psychological Association both contain information about how to properly cite and reference scholarly material.
Not all references are created equal. Peer-reviewed journal and conference papers are the gold standard, so most of your references should come from these sources. Books, edited volumes, and invited papers are also important and acceptable. Newspaper and magazine articles are usually not acceptable except to motivate the need for research in a certain area. For example, a Post article on the number of computer break-ins at the Pentagon could be used to motivate research on machine learning approaches for computer intrusion detection.
Furthermore, in the age of the Web, you must be very careful about using material from Web pages, simply because there are no checks and balances, no filters for credibility and veracity, for what someone can place there. The Web is an important research tool, but one that does not yet supplant traditional library research. Students in the past have used material they found on the Web as if it came from a peer-reviewed source. If you're unsure about a reference, bring it by, and we'll take a look at it.
The proposal should roughly follow the same format as the research paper. Here are templates in PDF and PostScript formats: [tmpl.pdf | tmpl.ps].