Every dancer wants to have a beautiful port de bras that looks effortless. What is the secret? Using your back! When you are performing, rehearsing, or just at the barre, focus on your arms coming from your back. Thus, they will always be correct. This makes them look effortless yet strong at the same time. For instance, when you do something like a grand jete, if you just stick your arms out, they are going to look stiff, and most likely your shoulders will go up. But if you use your back to move your arms, they will look soft and be in the right place. Try this exercise- next time you are at the barre, the whole time think of pinching a pencil between your shoulder blades, even when you lift your arms. This takes the focus off the arm muscles and forces you to use your back. When your arms are in second position, the same thing applies- press your shoulders down and squeeze your shoulder blades together. A bonus to this is the fact that your arms won’t get as tired! Your back muscles are much larger than the ones in your arms, so there is more support.
As far as your hands go, different schools teach different things. At the School of American Ballet (the official school of New York City Ballet) we were taught to have a more rounded hand with space between the fingers. This is so that from the audience, you can see all the fingers. In the first 2 divisions at the school (around ages 8 and 9) the students train with their middle and thumb fingers touching together. That way, their hands learn that rounded shape. Obviously, in a few years, they separate their fingers, but it gives them the idea of a rounded hand. Other schools teach different things, such as the Royal Ballet and Kirov based schools, but no matter what you are taught, it is important to make sure your fingers are relaxed. Not stiff and rigid-that makes you look like you have doll hands.
So, the moral of the story is, for both your arms and hands, keep them soft and pliable. Stiffness makes you look rigid on stage.