The standard format for headshot photos is black and white. The picture should be an 8-by-10 and an extreme closeup of the actor's face. In some cases, a color photo may be requested for certain modeling or casting agencies. However, if you don't receive any specific information concerning your headshot before the audition, it's best to present the photo in black and white.
It's best to staple your resume and letter of intent to the back of your headshot. This way, your photo is in full view, and your important information is fastened securely to the headshot so that it is not lost. If you include a letter with your headshot, explain why you want the audition, and the asset you would be to the production. Be sure that your headshot matches the work that is featured on your resume, i.e., have a fun and lively photo if you're auditioning for a comedy role.
Traditional head shots have a white border around them, which brings more attention to the black and white photo and allows casting agents to get a good look at all your features. You should also include your name at the bottom of the headshot in a font that is easy to read. Even though your name will be on your resume as well, including this important information at the front of the headshot will make it easier for agents and directors to identify you, which could get you one step closer to getting the audition.