My daughter Leah has been known to consume about a pound of haricots verts in a single sitting. Coincidentally (or not), she also looks like one of those skinny French beans.
“Proper” technique for cooking green beans (regular or haricots verts) is to blanch them in boiling water for about 2 minutes, then drain, rinse and cool in an ice bath (to stop the cooking). Then, you sauté the barely-cooked beans in butter and/or oil until just tender. This is not a bad method – especially if you want to blanch the beans a day ahead of time– but I have found that the extra steps (and dishes) are not necessary. Especially if you cook beans a lot – which we do.