Groom yourself. Get your nails done and cleaned up. Take care of your skin to keep it clear, get your teeth whitened or fixed, hair well maintained, pluck those eyebrows and work out so your body is in great shape. Make yourself the total package before you start anything.
Find a photographer. Look in the phone book, online or other places photographers advertise. Look through their books, portfolios and websites. Schedule a shoot date to get your zed card photos done. Bring several looks (outfits, shoes, hair accesories, make-up, etc.) to the shoot so you have a wide variety of photos.
Look online for a list of modeling agencies in your area or check out the Ross Reports, which lists agents for film/tv/modeling and more. Search through the listings to see who is accepting submissions. Also keep your eyes open for open-call postings online. Sometimes agencies will have an open call to find new talent.
Have your photos from your zed card shoot printed as zed cards. Send these out along with a cover letter to all agents seeking new submissions. Also take a zed card to the open calls you attend.
Show up to your meetings and calls early and dressed to kill. Look clean and fresh but as gorgeous as possible without wearing too much make-up. When asked a question, speak as clearly and kindly as you can. Be personable. Even if you're stunning, you still have to have some personality. When an agent is interested in you, they will offer you a contract. Read all the bylines well and make sure you understand it before signing. Good luck!