Practice along with some of the influential blues music from the past. The greats include Stevie Ray Vaughan, Eric Clapton and B.B. King. Learn the many nuances of the blues style include the rhyming style and the patterns that are utilized during the verses and choruses. The best way to start to become a blues singer is to mimic those who have mastered the style.
Go to open mic nights at blues bars and at other clubs where you can sing the blues. Most backing musicians will know the blues standards, and can play the basic blues patterns for you to sing to at a bar or club. Have at the ready, a list of songs you would like to perform, and give them the choice of song to play.
Visit a karaoke bar to start singing the blues. Karaoke bars have thousands of songs available, many of them in the blues style for you to sing to for practice or to start getting a name for yourself in your town. Pick songs that you are comfortable singing and don't worry about messing up, as the blues is not about perfection -- it is about feeling.
Learn to play the guitar to accompany yourself. Most blues singers also play an instrument such as the guitar or the piano. B.B. King is famous for his singing as well as his guitar playing. "Lucille" is always with him when he performs, and he uses the guitar to express his feelings and emotions along with his voice.
Start a blues band to begin your career as a blues singer. Put out advertisements at local music stores and on the Internet looking for backup musicians for your blues band. Start with a solid drummer and bass guitarist if you can play guitar yourself. If not, you will need a strong, well-versed lead guitarist to round out the band.