http://www.youth.gc.ca/eng/topics/jobs/cover.shtml
This website is extremely helpful on how to write cover letters, and also provide the key points on first impression to an employer. I usually use this website to write cover letters.

http://workawesome.com/your-job/how-to-write-a-cover-letter-that-gets-read/
This website shows how a cover letter should be written and also that it represents a critical component of getting your resume read.

http://owl.english.purdue.edu/owl/resource/723/1
This website have credible resources on cover letters and how it should help you with your research.

A cover letter:

• introduces you and your resume to an employer
• explains why you are writing or applying for the job
• details why you are a good match for the organization and the position
• demonstrates your abilities and helps to establish your credibility
• draws your readers' attention to specific qualifications
• provides a sample of your written communications skills
• explains when you plan to contact your prospective employer.

These were some of the key points from the last website and i do think that showing determination, demonstrating your abilities should or can drwaw your reader's attention.