After you have learned a sufficient amount about the company and where you would fit in, if hired, evaluate yourself and decide what you can bring to the mix. What skills and experience do you possess that will apply to the open position's specific tasks or goals? For example, if you are applying for a position in an environmental law firm, research its current cases and latest news. Maybe the firm is currently working on an air pollution case and you just happen to have worked on a similar project during your internship last summer. Tying in your expertise with the types of cases and work a firm deals with is key in a cover letter. Also, do not be afraid to congratulate your potential employer on current wins or advances within the company. Of course, be brief and professional about it; maybe throw in a quick line at the close of your letter. That way, employers know you are reading up on and studying their companies.
Be careful not to regurgitate information that the company already knows. For example, Googling a company's name and then copying and pasting a line from the overview on their website is not going to impress them. For instance, do not say, "Fulbright & Jaworski was voted among the ten best firms in the country for environmental law." A better choice might be something like this: "The experience and knowledge I acquired during my internship with environmental law firm Morgan, Lewis & Bockius, specifically with issues related to implementation of the 1990 Clean Air Act Amendments, can complement your company's notable and extensive work in clean air and water."
It is also vital that your resume reflect the research you have done on the company you are applying to. Evaluate your range of skills and employment history, making the proper adjustments to demonstrate that you are right for the job. Again, know what types of cases and work the company handles so you can keep this information in mind when narrowing down your sharpest, most relevant skills and most applicable job experiences. If you are applying for a position in a law firm, it clearly is not essential to mention your summer job at Burger King in 1986.
If you have a long work history, only reflect the last five to ten years of work, depending on how many jobs you have held. Since employers typically spend less than one minute perusing your materials, you are doing yourself a favor by omitting unnecessary and irrelevant information…or, rather, junk.
Craft your cover letter and resume carefully, so that by the end of reading them, the employer you've tailored them to believes you are the only one capable of doing the job.
See 6 Things Attorneys and Law Students Need to Remove from Their Resumes ASAP If They Want to Get Jobs with the Most Prestigious Law Firms for more information.