In a large skillet, heat the butter over medium-high heat.
When the butter stops foaming, add the green beans and salt.
Cook, stirring often, about 5 minutes.
Add the black pepper, garlic, and crushed red peppers.
Continue to cook, stirring often, for about 5 more minutes, until the beans are tender but not mushy.
The most important thing, in my opinion, is to avoid overcooking the beans. You want them to be tender. But they should still have a bite - much like "al dente" when cooking spaghetti. You definitely don't want them to be mushy or droopy.