1. Know what a cover letter is. 
In applying for a job, you need to know what a cover letter is so that you would be able to recognize its importance. The cover letter is actually the same as the letter of application, letter of introduction, as well as a transmittal letter. It is a letter that should always accompany the applicant’s resume, since not too many employers would consider an application without it. 
2. Read your cover letter several times. 
Prior to submitting your cover letter along with your resume, you should read it a good number of times. This is to ensure that you have already indicated all the necessary information in it. Aside from that, it can also help you condition your mind well if you get interviewed. 
3. Do not forget to check for punctuation and grammar. 
One of the things that can turn off an employer is when he reads a cover letter that has incorrect grammar and punctuation. Thus, you should not forget checking it for these couple of things. Keep in mind that aside from becoming familiar of the rules in using punctuations, you can also use tools on the web, as well as on your computer, which can help you check on your grammar.