Watch the Right-Hand Position online guitar lesson by Bruce Arnold from Guitar Physiology Survival Guide
While the index finger and thumb are holding the pick the rest of your fingers should be gently folded to form a loose fist. Commonly students will close their fingers too tightly, so make sure your fingers are folded enough to keep them out of the way of the strings but not so tight that you cause tension. We are working towards an open playing position, where you don't rest your fingers on the instrument. This idea of resting fingers on a pick guard is commonly used in older players. The logic behind it is that it gives stability and an anchor to calculate where you are as you move from string to string. In reality it completely messes with your ability to play from your forearm, it's an unnatural position for your body and limits certain types of hybrid picking styles that can be useful. Again players have played their whole life with this technique and may swear by it, but it can cause problems due to its inflexibility.