There are plenty of people the will discourage mass mailings to agents or casting directors and sometimes they are right. There are many 'tips' like writing "requested materials" on the envelope or even folding is the shape of a star. It's important to know one things when it comes to submissions, every day thousands of Actors submit Headshots and Resumes to Agents and Casting Directors who get hundreds of Hedshots and Resumes across their desks everyday. If they are looking for someone or something you can bet they will sift through every envelope and postcard. If they aren't looking, then they won't. Mass mailing your Headshot is a game of chance and hope. You hope by chance when your envelope reaches their desk they are in the mood to open it. But once you have your Agent and you have started meeting Casting Directors what should you do? How should you stay in constant contact with those that are interested in you already. Did that Casting Director that you worked for last year book another show? Send them a note. Did that Casting Associate who called you in get their first gig as a Casting Director? Send them a really nice note. Of course you should always include a headshot, maybe one that's close to what they might be looking for in their new show. It's important to realize that Casting Directors, Agents, Managers want you to do well want you to be the one. They need you and you are the answer to their problems and most people like working with people they like to be around. Making a film is like inviting everyone in the cast and crew into your kitchen for 6 months. You don't need everyone to like you, just the ones that do. Send postcards individually and really see the difference.