You should feel great wearing a good dress shirt, not like a kid in his dad’s work clothes. Use a military-style tuck to prevent billowing, or “blousing”, around your belt line.
Australian styling and fashion blog A Good Man provides five steps towards tucking in shirts to avoid having them blow out and hang over the top of your belt, making it look like you’re carrying water for a long desert trip. As noted by A Good Man, and seconded by the Put This On post that linked to it:
It helps to think of this method as placing your pants over your shirt, rather than tucking your shirt into your pants. Obviously, this technique only works for shirts that mostly fit, and just have some excess fabric in the body. If the shirt is a size (or more) too large, this method won’t work and it will need to be altered by a tailor to make it fit correctly.
In short, you just pinch excess fabric at the sides of your waist, then pull up that fabric and fasten your belt line around it.