Prepare a head shot
Find a commercial head shot for yourself. Get in touch with a professional photographer who has some experience in actor head shots. After that, set a meeting so that he can photograph you. You should be aware that a commercial head shot is different from a theatrical head shot by a far margin. It is important to keep a happy facial expression and do not be serious in the picture under any circumstances. During your time with the camera person, you can also ask a favour from him to take pictures of you for a theatrical head shot in the case you look for some theatrical work.
Select the best picture
Analyse all the photos carefully and choose the commercial head shot you think is the best. Photographers generally provide the actor with a CD or send an email with photo attachments. Remember that both these consist of all the pictures from your photo session. Then visit a photo development facility that specializes in actor head shots and lithographs. Get a lot of hard copies and maintain the digital version after you have made appropriate adjustments with it.
Find an agent that can represent you
Get a listing or commercial agencies and agents. These will tell you of which agents and agencies take care of commercials side of the business or theatrical. From this list, shortlist the agents and agencies you want to work with. Once you have done this, email your head shot to these agencies and agents. Also add a resume at the back of your head shot. Write your contact number, height, eye colour, hair color and weight in the resume. Do add any prior work you have performed before the commercial.