Try singing longish notes (not overdoing it) on any vowel you feel comfortable with, and varying the position of the tongue in your mouth until you find a place where you feel comfortable and you are happy with the tone of your voice, then practise recreating it at random moments - eventually you learn how it feels enough to make that same tone with other vowels.

Always sing with the throat as open as possible - imagine how open your throat feels when you yawn, and try to open it like that when you sing.   

As everyone else says, practice is a key thing, and listening to good singers, especially live, can give you ideas about breathing and the kind of sound you may want to make - you don't have to copy other people, but you can subconciously pick up a lot about technique from watching others, and singing with others is very helpful too, both from the point of view of tone quality and intonation.