The cover letter is your introduction to a prospective employer. In fact, a resume should never be sent without one. A cover letter presents your resume to the reader and expands on points that may have been covered briefly in the resume.

A good cover letter is brief, to the point, and no longer than one page. If a reader takes no more than 30 seconds to read a resume, even less time is spent reading a cover letter so it's worth investing the effort write it well. Here are some pointers that can help:

1. Communicate clearly in your letter what you are looking for and give a brief summary of your skills and experience. Give the reader enough information to persuade him or her that it's worthwhile to read your resume. Since all jobs require effective communication skills, the cover letter is one way to demonstrate those skills. Clear communication is especially critical if the person reading your letter is not a scientist.

2. If you're in the midst of a full-blown job search, resist the temptation to develop a generic cover letter. Whether you are responding to an advertised position in Chemical & Engineering News or a position advertised on a company's Web site, tailor your letter to address the advertised requirements. Add value to your letter by highlighting achievements that are related to the position you are applying for—but don't restate your entire resume.

3. Personalize your letter and mention why you're interested in working for the company. If you can, include pertinent information such as recent acquisitions, new projects, or company milestones. Were you impressed by any of their products? Show the company you're serious about working for them. Whenever possible, address your letter to a specific individual.

4. Don't provide salary information if the ad does not specifically request it. If the ad asks for salary requirements, avoid stating a specific number. You cannot negotiate a salary unless you have an offer in hand and generally, statements like these are used to screen candidates in or out. For example, you could write, "My salary requirements are negotiable depending on the position requirements." Your goal is to negotiate a salary based on the job you're applying for, not what you are currently earning now.

5. As in resume writing, check, double check, and triple check your cover letter for typos and grammatical errors. Then ask a friend to check it again for you.

Anatomy of a Cover Letter
Opening Paragraph. The first paragraph of your letter should indicate how you learned about the job opening. If you are responding to a newspaper ad, reference the newspaper and the date the ad appeared. If you are sending your resume at the suggestion of a specific person, be sure to include that information.

Second Paragraph. Here is where you add the value to your resume. Provide the reasons why you're the best candidate for the job and include specific accomplishments from your resume. A bulleted list may be more effective here than a straight text paragraph.

Third Paragraph. This is the final paragraph of your letter. You can mention that you will follow up in a week with a phone call to set up an appointment but only if you intend to do so. Be sure to provide a telephone number where you can be reached.

E-mailing Your Resume?
If you will be sending your resume by e-mail, the same rules generally apply when you write your e-mail cover letter. Since you will be attaching your resume to the e-mail, your message should likewise persuade the reader to open the attachment.

The critical difference between a hard (paper) copy and e-mail cover letter is that you will need to craft a specific subject line for the e-mail to let the reader know that it's not a junk e-mail. Given the high volume of e-mail that people receive on a daily basis, it's simply common courtesy to let the reader know what the message is about. For example if you are sending your resume to someone you met at a conference, the subject line could read "Follow up: Resume of William Charles".

When you use e-mail to send your resume, invest the same time and effort to carefully craft your letter as you would a hard copy. People will still print out and save e-mail messages so you want what you write to reflect well on you.

Tips on Resume Preparation, published by the ACS Department of Career Services, is a guide to help you make the best first impression possible on a potential employer and includes sample cover letters.