Move to New York City if you don't already live there. Once you get there, find a cheap apartment and become a waiter or waitress. Read Variety, go to auditions and wait for your big break.
Take acting, singing and dancing classes while you continue to go to auditions. Don't get discouraged by rejections. Keep trying no matter what, and keep striving towards your dreams.
Make every opportunity count. So what if your first job is in the back row of the chorus behind a potted plant where no one can see you. It's a foot in the door, and that's all that matters.
Work you way up to becoming an understudy. So what if the leading lady or man mysteriously becomes ill or falls down a flight of stairs, it's your turn to stand in the spotlight and sing, art or dance your heart out. Or if you don't want to go that route, continue to work hard and soon directors and casting agents will start to notice the kid in the third row with all the talent.
Rehearse, rehearse, rehearse once you've finally gotten the part you know is going to make you a star. Then, on opening night, give the performance of your life. Act surprised when people tell you how wonderful you are, be gracious. Then remember how hard you've worked to get to this moment so that it really sinks in.
Pray that your producer believes enough in the show and your performance to invite each of the eligible Tony voters to your show, since that is what gets the ball rolling on you winning one.
Continue to pray that they think you're worthy of a nomination, and once you get one, lobby like the devil to win. Place ads in newspapers (especially industry trade papers), invite Tony voters to parties and dress like a king or queen on the night of the Tony Awards. Then, accept your prize as if it was a complete surprise, and pull out an enormously long list of people you want to thank.