Sing anywhere you can. Local fairs are particularly good. Join a band and sing at as many regular gigs as possible. Gather a local following and release your music locally, then invite music industry professionals to attend your shows. Send them invitations and a demo. Regional success will make you more attractive to professionals in the music industry, which can translate into a contract that puts you on the road to fame.
Make a mailing list of music companies that fit your style and target them. Put together a promotional package that includes a short bio, performing credits, a three- to four-song demo that demonstrates your range, a short performance video, and a few glossy 8-by-10 shots. Music industry professionals want to the whole package. They want to know what you sound like, how you play to an audience, and if you have what they consider the "look" of a star. Your promo package gives them all of that.
Launch your own website and sell your music online. Include plenty of samples of your singing and dedicate a section of your website to showcasing your work to interested music producers and agents. Make it easy for any interested party to request one of your promotional packages.
Consider signing with a talent agency. A good talent agency will find you work as a singer. The more singing engagements you do, the more you will be recognized as a professional singer. This makes you a more valuable commodity to music executives, which can lead to a contract and a distribution deal that will put your name in bright lights.