One of the most important steps to take when turning in your résumé and cover letter via email or an online submission is to give it a proper name. Too often, people's résumés and cover letters are given the generic name "résumé.doc" or "coverletter.doc." Step it up a notch and personalize the files by adding your name and renaming them to "JaneSmithRésumé" and "JaneSmithCoverLetter.doc."
Remember, the hiring manager receives many submissions. If they're saving the files to their computer, you're saving them the extra step of renaming the documents.