You've worked hard on your resume, Now, don't overlook the cover letter. It doesn't matter what type of industry you're in or to what career you aspire -- in nearly every situation, a cover letter can help to highlight your skills and make your application materials stand out from the pack. The exact details may vary, but all cover letters include a few key sections.
Chances are you've included a resume with your contact information in your application packet, but you don't want to leave anything to chance. As such, it's important to start off the cover letter with your contact details. At the top left or top right of the page, type your physical address, then your city, state and zip code on the next line. Under that, include your phone number, and possibly, your e-mail address under that. Then skip a line or two, put today's date, and then type a formal salutation to the addressee; "Dear Hiring Manager." Even better, get the person's name: "Dear Anna Smith."
Before you dive into any details, the addressee is going to want to know why you're writing. If you're responding to a formal job posting, name the job for which you're applying and mention how you found out about the job. If a current or former employee has referred you, be sure to mention it. If you know the referrer through a professional connection, mention the connection in this first paragraph, as well. This section does not need to be dry and boring; try to use key words or descriptors used in the job posting that apply to you, or find other ways to hook the reader in. If the job has not been formally posted, state the job you are inquiring about, or the general section or department with which you want to work.
The second section is the meat of the cover letter, and the part in which you're going to need to sell yourself. Review the job posting -- if any -- to get information on the employer's ideal candidate, and then be sure to mention any traits or experience you possess that match the employer's ideals. Your resume will list your education and work experience, but you can use this paragraph to state how those experiences make you a great candidate. Try to focus on a few key details that make you a great candidate, and expand this section to a few short paragraphs, if need be. The cover letter is typically no longer than one page, so expand or shorten this section accordingly.
In the final paragraph, restate the job for which you are applying, and then include any follow-up details the employer needs to know. This may include your available hours and days for interviews, letting the employer know when you will be available for work, or informing the employer that you will be in town and available at a certain time. More bold candidates will state a specific date and time in which they will contact the employer -- but if you do this, be sure to do what you say you will do. Following that paragraph, skip a few lines and type a formal sign-off such as "Sincerely," or "Regards," and then sign the letter.