Get accepted to a highly ranked drama school. For example, the Actors Studio at the New School in NYC can offer an actress a wealth of opportunities, as well as looking great on your resume. By attending a respected drama school that offers a strong program, students have both an environment to hone their craft, as well as to showoff their talents. Many drama schools put on performances for the public throughout the year. As actress can also network with other actors, directors and screenwriters in search of potential projects that her peers might be working on that she can try out for. Collaborating with fellow students on their low-budget film projects is a great way to get to know people that can aid your career in the future. This might not sound like a way to get "noticed" but if a film does well at a film festival, in part, due to your stellar performance, then you might soon find yourself fielding offers from agents and directors.
Get an agent. It is often extremely difficult to achieve exposure or get your foot in the door without professional help. A good agent has connections. He will be "in the know" and privy to insider information which might offer you access to the more choice auditions that someone without an agent wouldn't get or even hear about.
Take on challenging or daring roles. Be willing to take a risk even when it scares you. Obviously this doesn't mean endangering your health, but rather doing something that shows your commitment to a role. You might also choose to audition for a role that is difficult, either due to the complexity of the text or even the degree of emotional vulnerability required by the actress. Don't let fear of the unknown keep you from doing something you know you can do.
Stand out in the crowd. Be different, be distinct. That is easier said than done but it's certainly possible. This isn't just about hairstyle or wardrobe. For example, you might develop certain skills that set you apart, like sword fighting or being able to act in a full range of dialects. As long as it's something you believe jumps out from your resume, or audition, to catch a casting agent's or director's eye.
Be persistent. Few actresses achieve fame or success overnight. Perhaps even more so than other careers, actors must be willing to put in the time and effort to build a resume that will lead them to bigger and better roles. While it is possible to snag a juicy role that propels you to fame and fortune in the blink of an eye, it's much more often the case that you will have to work hard and pay your dues to accomplish your dream.
Consider joining a union that represents actors such as SAG (Screen Actors Guild), or AEA (Actors Equity) that represents stage actors (see Resources). With membership, you are guaranteed certain rights as a performer, including a specific wage required by union guidelines.