Letters and Applications
Together with your photographs and resume, a cover letter is your calling card. As such, it's important to set the right tone and create a good impression.
While it's true that a good letter can really do you favors, it's also true that a bad, poorly presented letter can result in your application being dumped in the bin or filed in the eternal filing cabinet. Agents, directors and casting directors receive a mountain of unsolicited approaches and won't be able to devote more than a few moments to each, therefore it's essential that you don't give them reason to dismiss your approach. It may simply be that you're not right for a role or for their books because of your physical characteristics and experience or the requirements of the role, but you'll be doing yourself a disservice if you send off a letter that's unprofessional in appearance and content.
You might think that spelling and grammar are irrelevant, the real substance is in your acting ability. Yes, once you're on the stage or in front of the camera... only you've get to get on stage first and you might have ruled yourself out of the selection process by writing a poorly phrased, poorly presented letter riddled with mistakes.
Given that there will be dozens, hundreds or thousands of other letters you might wonder how you can distinguish yourself, set yourself apart from the others. The tone of a letter is one of the most important elements and yet one of the hardest to get right. You don't want to sound sycophantic, arrogant, outlandish or zany. Including a keepsake or memento or some other such wacky device might raise a momentary smile in the office... it's also likely to land you in the bin, or worse, end up being circulated to others with the heading "Look what this guy sent me!". (There are no doubt exceptions to this but they'll be in the minority.)
Be professional, find out the name of the person to whom you're writing (and make sure you spell it correctly!) and address them by their full name rather than by their first name or title. Be yourself in the letter but keep in mind that yours will be one of many letters and that the agent / director won't have the time or patience to read an essay. A letter should be a couple of clear, succinct paragraphs including why you are interested in the role / agency and why you think you're suitable and should be considered.
If accompanied by a headshot(s) and resume, they'll have an idea of your look and your career to date, so in your letter don't simply parrot what the resume says. Writing a good letter is a fine line between being arid / uninformative and irritatingly verbose and/or self-aggrandising. When writing a letter try to think how it will come across to the reader, a person who doesn't know you. It's a good idea to run your draft by a friend or colleague for a second opinion before sending it.
Write in the first person singular (I), adhere to the usual rules of grammar and letter writing. A standard letter will often start with the recipient's address (at the left-hand side of the paper) with the date writing (usual format 12th May 2005) beneath followed by the greeting (Dear Marjorie Cruickshank,), the body of the letter and concluded Yours sincerely, with a space for your signature and beneath that your name (printed). You can, if you wish, include your address at the top right of the letter, though there are no hard and fast rules about this and your address should be included on your resume.