When writing to Directors, Agents, Casting Directors etc, there are several important things to consider.
Know who it is you are writing to.
Wherever possible avoid sending out letters that are headed up Dear Sir or Madam. It shows very little thought on your part if you don’t invest a small amount of time to find out exactly whom you should be writing to. In this day and age many theatre companies have websites (some even display casting information), use the information on the site to try and find the name of the Casting Director or Director of the project you are showing interest in.
Formality
Although it is usually acceptable to use first name terms in the industry, do not make the mistake of being overly informal with your letter writing. Very informal letters betray a level of unprofessionalism on your part. Writing to an agent or other industry professional is NOT the same as text messaging your friend. Even if you are using email you should still construct your message as though you were writing a letter. I have received emails that read
“hi I waz jus wondring if you have any jobs going???”
Spelling and Punctuation
The above is a perfect (all be it extreme) example of how poor spelling and punctuation can leave you looking bad. Good spelling and grammar demonstrate a basic level of intelligence and with most word processors and email software having a spell check facility there really is no excuse for it.
Content
Although most directors agents etc don’t have the time to read a three page essay about why you “are the right person for the job”, try not to be overly brief. Your letter (combined with you photograph) should indicate why you might be worth considering for a part and what you can offer the production. Personally speaking, if I get a sense of personality from the letter (and it is well written) I will almost always offer that individual an audition.