There are a lot of singers here at Santa Fe in the Road Scholar group, most of them more successful than I was.
At breakfast I was promoting my idea that you could simply teach two things to students of any age--breath support and the legato.
Nobody agrees with this. To most people the legato is not anything. But for me these two things go together--you must learn to connect the notes, to carry the phrase across the consonants and even any short rests that may appear. It is this skill that validates the success of the breath support.
Sing music--not just notes, and everything about your singing will improve. For me this is my most deeply held belief.