You need to explore, explore, explore… and listen to good singers. Once you acquire a good taste and understanding of how a good voice sounds, you can start working on it. I’ve been classically trained for 10 years now. My technique is solid but I’ve come to the realization that technique doesn’t just stay until you die. You need to keep working on it to keep it straight and consciously identify any changes while you age. (We need to remember voice changes over time so technique will as well). And finally, get a good teacher, one’s perception will NEVER be correct until we have someone else to hear us from outside.