Every submission to an agent or casting director or submissions for specific projects should always be accompanied by a cover letter. This is a method of introducing yourself and piquing the interest of the person on the other side. Cover letters shouldn

Packaging

For a cold snail mailing, you can print out the letter separately from your headshot and resume. If you would like to include a letterhead, make sure that it matches your resume. For online mailings and submissions, you can place the cover letter in the body of the email with your headshot and resume attached or copy and pasted below your introduction. 

Information 

A cover letters for an agent is definitely different than one you would include in a submission. A cover letter you send an agency should include several pieces of information:

• Who you are
• Why you choose that agent/agency in particular (Was it a referral? Do you know their past projects? Etc.)
• What type of representation you’re looking for (commercial, theatrical, legit, etc.)
• Are you union or non-union ready to become union
• Why they should be interested in you (Did you just book a big project? Do you have a special skill? What is unique about you?)

For example: "After I met with casting director John Doe over at Casting Agency X, he suggested I get in contact with you about legit representation. I just recently booked a national Geico commercial after auditioning for them. I am a SAG actor with several legit credits. I will follow up with you next week by phone to see when would be a good time to meet."

A cover letter for a submission should include where you heard about the project (if you’re not submitting straight from a submission site), if you are union/non-union, why you would be a good match for the role, and anywhere that they can find more information or a reel from you.

For example: "I saw your notice on Backstage.com and am writing to submit for the role of Jane in your Feature Film Project. I just finished filming Short Film Project and am looking for a big project to be involved with. You can watch my reel at Youtube.com/me. Please feel free to contact me for more information. I look forward to auditioning for you."

Regardless of what it’s for, you should be brief and to the point. Include only the information you think would help sell you as an employable actor. If your letter is too long or too abstract then there is a strong possibility that the letter will be left unread.