GET TO KNOW YOUR VOICE WELL
By this, I mean how it works, how it sounds and what it feels like.
Do you speak clearly or do you speak constantly with a 'crack' in your voice?
Do you whisper more often than is necessary?
Talk as naturally as possible. Whispering is harmful to your vocal cords as it causes tension.
Do you shout? Do you sing with an artificial voice?
Do you constantly sing in falsetto?
Are you trying to imitate other singers by producing a voice close to theirs even though it is uncomfortable?
GET TO KNOW YOUR RANGE
Every person has their own natural range in which they perform best. Find out about yours. One way to find out is by having singing lessons.
If you have a distinct register break in your voice which is easy to hear, don't panic. This is quite normal. Certain styles of singing make use of these sudden register shifts but proper training aims to equalise the quality in the different registers so that there is a smooth transition from one to another.