"If you have a good cover letter, people will definitely take notice," says Larry Griffin, partner of Bridge Partners, a New York--based executive-search firm. "It's the first tool that you, the applicant, can use to get the reader interested in delving deeper into your background."

While the position and the company to which you are applying ultimately dictate which aspects of your personal life and professional career should be highlighted, here are five Don'ts to make sure your cover letter doesn't keep you from that ideal job.

1. Keep it short. True, the cover letter is your opportunity to introduce yourself to your future employer, and there is an inclination to be long-winded. Remember, managers are pressed for time and are often sifting through hundreds of applications. Keep your cover letter short and to the point. "It's most important to get the salient points and entice the interviewer to probe further into the résumé," says Griffin. "Write a cover letter that is targeted to a specific industry and position."

Decide what is important to you and how comfortable you are with the information you are sharing. Alan Muir, executive director of the Career Opportunities for Students with Disabilities, says it is up to the individual to decide whether he or she is comfortable disclosing a disability. "It all depends on the individual [and] what they are most comfortable with," says Muir. "There are others who are self-advocates."

2. Don't be careless. Being sloppy is the most obvious way to have your application tossed. Assuming the spelling of a company's name or the gender of your interviewer are both major deal-breakers. "If you have any typographical errors, it says a lot about you, the individual," says Griffin. "Take time to do your research." Researching the company's site will also ensure that your facts are in order.

Read Ask the White Guy to see how spelling errors can really hurt your chances.

3. Don't assume the office culture. In most guides to "getting your ideal job," there are countless cover-letter examples that include the sentence "I would be a perfect fit for your office." Wrong! Assuming the office culture without having interacted with the culture can ultimately result in disappointment. "Often, candidates step out on what they think the culture is and assume they are a good fit for it," says Steven Hunter, chief diversity officer at Belk Inc.

Does that culture embrace diversity? The only way to know for sure is if the company is listed in The DiversityInc Top 50 Company for Diversity^®. Otherwise, it may not be the type of place you want to work. If it's a smaller company (the Top 50 requires a minimum of 1,000 U.S. employees), do as much research as you can to see if it's a place where you would "fit in." Do you really want to be a barrier-breaker?

4. Don't revert to cheap flattery. Chances are any overzealous compliment about the company you craft will come across as fake. Companies, at least the good ones, know what they do and that they do it well. "If you are approaching a smaller company and you have done your research on the company, showing that you are knowledgeable about the industry or the company could be a good thing," says Griffin.

Avoid being too personal with your interviewer. Assuming a level of familiarity because your interviewer is of the same ethnicity or gender can be off-putting and can negatively affect your application.

5. Don't oversell yourself. "At the junior level, you have not had a tremendous amount of work experience and exposure; you are what you are," says Griffin. "To oversell yourself shows that you are not realistic in your goals." Instead, sell your experience, he advises. Highlight your skills and accomplishments and things that have gone well in your professional life. Always tell the truth.