Sound Good when Singing - Vocal Exercise
The best way to sound good is to be natural. Be Yourself , don't try to overdo things. When you try to bring in the extra power, then you will sound un-natural and often shrill and sharp which is not good on ears. As amateur Singer you will tend to imitate what you hear. This will make you sound artificial. You will not be consistent , somedays you will sound good and people will appreciate you , somedays you will do bad and will shake your confidence. They key is to be in control, Sing in your most comfortable vocal range, since the songs you are comfortable with. When you reach a level of perfection, then you can take up other songs and try different things.
This another video explain how to check if you are not sounding good. It uses NG sound exercise to explain how to sing with flow and sound better.