The best solution is to take private lessons from teachers or to apply for courses in the school of music (College of music) for singing and development of musical hearing. A similar option is to order a video course, audio course from the teacher via the Internet and do it yourself. Minus the kind of activity that you will not be able to ask questions on the fly, requiring permission from the professional person, and all the tasks you have to solve yourself.
Get professional installation and a large karaoke selection of songs for performance. Sing favorite songs frequently. Try not to shout over the music and listen to it, to adjust his voice to the tune. Change the key of the next song for easy execution.
Purchase musical keyboard instrument: piano, digital piano, synthesizer (can unprofessional cheap). Ask family to press the various keys. You have to repeat their sound your voice. Or do these exercises themselves. Over time complicate the task. Press the two keys at the same time and try to sing both sound. Then three keys and so on.
Using the keyboard tool, ask loved ones to press some key on it, themselves at this time turn away. Now go to the tool and try to find the key, the sound which you just heard. Task simple trying to find the sounds of the two keys pressed, three and so on.
Sing in unison with any instrumental accompaniment. This exercise may bring the hearing to a perfect.
Study notes and propagate their sight-sing single-voice exercises, guess lost notes, intervals and chords. Such exercises develop the hearing professional musicians in the music educational institutions.
To develop a musical ear even sitting by the computer. Download any kind of music program examiner. Such programs, if you work with them regularly, not only develop the ear, but also check your data, give results, helping to consolidate their knowledge.