Like what toomuchtimeoff said, record your singing from time to time and listen to them. Start accepting how awful or how nice your voice sounds.
Listen as much as you sing. Listening provides great help to hearing pitches, feelings of songs, that will benefit your singing.
Try to get more performing opportunities. Be it in front of your family, or friends, or at the karaoke hall, or at dinners, put it all out. Though you may suck initially but rest assure that you'll improve through time, when you get bolder.
Only through practical experience, one will learn.