Practice, practice, practice.Sing for the love of it.I found it helpful to sing in a large choir, (Not miked) with many voices in each section. Find the range most comfortable for you and sing in that section. I found the best training came from singing the harmony parts (alto and tenor)which often have fewer interval leaps, more repeating notes and step-wise movement. Accentuate the positive- a lovely tone, for example. Don't stop!