How do I easily and quickly expand my vocal range?

I am a 16 year old male,and the lowest note I can hit effortlessly is the B under middle C, and the highest is the G above the middle C. That isn't even one octave! I can sing, I mean I have a good voice, but I want to sing songs "effortlessly." How do I easily and quickly expand my vocal range? Please include tricks and helping with both lower, and hitting higher notes.