Every cover letter varies from post to post, from job to job and from industry to industry.
Don't repeat your resume: Use the cover letter to showcase your personality, not as a summary of your resume (they already have that, and would not appreciate reading the same thing twice)
Keep it short: Less. Is. More. Three paragraphs, half a page tops.
Address nobody: If you are unsure who to address it to, leave it, but nix the bland and generic "Dear Hiring Manager" or "To whom it may concern"
Send it as a pdf: If you are sending your cover letter and resume online, why not send it as a pdf. Not everyone might be able to open a .docx or .pages file, but everyone can usually can open a pdf.
Never ever ever write "My name is _____ and I am applying for ______" They already know that. Don't sound inexperienced.
Close Strong: Finish of quickly, anything more than a few seconds is rambling.
Why you want to work for the company
Unique value that you - and only you - can bring to the role
Professional traits that might not be obvious in your resume
Connections between the job announcement's requirements and qualifications and your credentialsYour goal, again, is not to re-present your resume information, but to sell yourself and ask for an interview
One other point: If there is some obvious question that needs to be answered or a condition that needs to be addressed, do it. For example, if you are located in a different part of the country, you should state, "I am willing to relocate for this position."
Covering Letter Tips
Why resume should be tailored by Resume master?
A resume should be flawless and sorting of section varies from profile to profile.
There are lot of companies who showcase themselves as resume writers/ writing company. Ask them the differences between Cv and Resume. By claiming as resume writers most of them will prepare you a Cv instead of Resume.
Resume should be Clear, concise and grammatically correct.
Your industry exposure and key achievements should be presented in the right place.
Your work experience and strengths should be highlighted in bold.
It should be attractive with better readability.
Simple format and consistency is maintained throughout.
Proofread it. Twice. Because errors on your resume reflects poorly on your attention to detail.
Let someone else proofread it. Twice. Because it's difficult to find your own mistakes. Use a simple format. You want your information to be memorable, not your layout (unless you're a graphic designer or artist).
Use short, concise sentences. Too much text overwhelms a reviewer's eyes. You only get a few moments of their attention, so make your strong points stand out.
Include your coursework and academic projects. Don't be hesitant to do so, especially if you have no work experience. What else are you supposed to put? Include any charity or community service work. Sometimes people help with projects for a family member or religious organization, don't be afraid to use that.
List your achievements. High grade averages and test scores never fail to impress. Low grade averages and test scores should never be spoken of. Ever.
If you have any work experience at all that can give you a positive reference, list it. Showing you're not afraid to work, even at unrelated jobs, shows dedication and responsibility. Not all recent graduates have that.