When you are applying for a Job, make sure you have a good covering letter attached with your resume.

Don't make the reader guess what you are asking for; be specific: Do you want a internship opportunity, or a permanent position at a particular location; are you inquiring about future employment possibilities?

Be Specific: Tell specifically how you learned about the position or the organization — a new paper advertisement, a web site or through some other source. If some one in the company has refered you, it is appropriate to mention the name of someone who suggested that you apply.

Be Convincing: Convince the reader to look at your resume.
The cover letter will be seen first. Therefore, it must be very well written and targeted to that employer.

Call attention to elements of your background — education, leadership, experience — that are relevant to a position you are seeking. Be as specific as possible, using examples.

Reflect your attitude, personality, motivation, enthusiasm, and communication skills.

Provide or refer to any information specifically requested in a job advertisement that might not be covered in your resume, such as availability date, or reference to an attached writing sample.

Indicate what you will do to follow-up.

In a letter of application — applying for an advertised opening — applicants often say something like "I look forward to hearing from you." However, if you have further contact info (e.g. phone number) and if the employer hasn't said "no phone calls," it's better to take the initiative to follow-up, saying something like, "I will contact you in the next two weeks to see if you require any additional information regarding my qualifications."