An effective cover letter answers some very tough questions. You have to think like an employee and ask yourself questions that they might ask if you were to submit a job application. Think of the kind of things that they might ask you during a job interview. Think of as many questions as possible and then take note of the answers. Then write down these answers as part of your cover letter.
A lot of people, who write cover letters for the very first time, make the mistake of writing a generic one that essentially covers a wide spectrum of things. However to give yourself the best chance of being noticed by employers is to write one that is specific to each job. Make sure that you answer questions that a particular employer might be asking.
An often overlooked step when writing a cover letter is not specifying exactly what position it is that you are applying for. Many times people will submit their letters along with an application that pretty much says, "I'll work in any available position". So even if you do happen to get hired by the employee, chances are that you will not like the position that they put you in. So the best thing to do is to let them know exactly what it is that you want. Tell them what position it is that you are seeking and list your qualifications.
An essential part of getting yourself remembered and recognized from a crowd of others is to make sure that you follow up on it. Give the management team a call and politely ask them if they have reviewed your letter. Be sure to leave them with your name and phone number so that they can contact you. If you really want to stand out, give them a call or talk to them before you submit your letter. Build up a relationship with the management team and make them aware of your presence.
By far the hardest part of learning how to write a cover letter is reviewing it. Make sure that you go over everything carefully to ensure that there are no misspelled words and that you mentioned all your qualifications. Also make sure that you do not list things that have become quite cliche and have become quite ineffective at giving a good impression. Only list things that you feel your employer is actually looking for in a good candidate.