A recruiter would rather talk with you during the day, so if you can take calls at work, include a work phone number. If a beeper is the best way to reach you, be sure to note that number in your resume and cover letter, in case they become separated. If your address changes during your job search, send another resume and cover letter for the positions that interest you. A recruiter won't bother to change data on your first version. The first paragraph of your letter should state how you learned about the job opening.
Most companies keep records of which sources are best at attracting promising candidates.
If you saw the job in the classified ads, mention the newspaper and date the ad appeared. State your objective and the specific position you're seeking. Recruiters work too rapidly to guess your objective. If you've researched the company, be sure to mention why you're interested in it. Drop a name only if the person appreciates your work and will speak highly of your abilities.