Basic guidelines on how to write a cover letter for oDesk?

•    Do not include contact information in your cover letter, like your email address,
  
  chat ID or phone number. This is a violation of oDesk policy and makes you an easy target for an unscrupulous client. You are free to share contact information when the client invites you to interview.
•     If you include a greeting, find a gender-neutral way to say hello, such as "DearHiring Manager," or use the client's name, if they have mentioned it. Refrain from the use of a greeting that starts with "To Whom It May Concern" or "Dear Sir." Neither adds any value, and they may even offend some clients.
•  The first sentence offers the strongest, briefest summary of a contractor's qualifications for the job and is visible as the client scans the candidate list. Make it as compelling as possible.
•   Use a cover letter specific to the job post. Never use the same cover letter repeatedly, even if you fill in the blanks with specifics for the job at hand. Just as you can tell when an client posts a template job description, an client can tell you when you use a form cover letter. If you do not put in the effort to write a custom letter, they are unlikely to take the time to interview you.
• Answer specific questions, or include the same keywords the client put in the job description, to prove you can follow directions. If the client asks for contact information, or otherwise violates policy, you should flag the job as inappropriate. 
•  Provide direct links to relevant examples of your work whenever possible. Make sure you add them in your portfolio, as well.
•   State your availability, such as when and how much you can work. Explain what kind of commitments you have to any other oDesk contracts or regular clients. 
•  Close by repeating your interest in the job and your understanding of the client's priorities.
•   Keep your cover letter clear and concise, keeping it to no longer than three to four paragraphs.

Example#  Cover Latter

Search Engine Optimization

Dear Hiring Manager,

I am Expert in White Hat Search Engine Optimization (SEO),

I have 5+Years of Experience in Sear

ch Engine Optimization (SEO), Online Marketing, Link Building

ETC...... I feel that I am an exact match for this position after thoroughly reviewing the job description,

required qualifications, and preferences. I can get your site in Google top ten results.

I have huge collection of high pr sites for back linking and link wheeling,I will use google most recently

updated algorithm’s strategy.

Waiting for you Kind Response....

Regards,

(Your Name)