Research local acting classes and join one that matches your needs and skill level. Check out your community college's theater department for low-cost options; consider becoming a theater major to gain experience in everything from directing to set construction. Many acting schools allow students to take an introductory course for free; take advantage of these offers to find the best fit.
Once you have started learning about the acting craft, put your knowledge to the test by auditioning. Check local theaters' websites for upcoming auditions. Many theaters hold auditions only a few times a year, so make sure to mark your calendar. Community college theater departments also hold auditions several times a year; in most cases, these are open to the public. For audition opportunities all over the world, check out mandy.com.
Create a professional acting resume and get a head shot. After you have gained some experience by participating in local theater or even by doing some movie extra work, start building your resume. Don't forget to include training information. Your head shot will be your "calling card," so make sure to find a reputable photographer. It is important to feel comfortable during your photo session so you look your best. Get enough rest the night before your shoot, and ask your photographer for clothing color recommendations prior to arriving at the studio. A makeup artist may be available at an extra cost.
Join networking groups, both online and in person. The support you receive and the contacts you make will be important as you build your acting career. Meeting up with other actors will give you the chance to hone your acting skills and stay current in your field. If you live in Los Angeles or New York City, check out the message boards on backstage.com. Subscribe to industry publications such as "The Hollywood Reporter" and "Variety."
Get an agent. An agent can submit your resume and head shot for auditions that you may not be able to find on your own. Be careful not to sign with an agent who asks for money up front---a reputable agent makes money only when you do.