Most people tend to pick from their wrist, but whether or not you do, it's important that your wrist be in the right position, or your picking will never be as good as it could. Some people instinctively position it right, others need to be corrected. If you still don't think you've got picking down, you might be of the latter.
When you twist your wrist, you're actually moving muscles all the way up your forearm, wrapped around two long bones, your radius and ulna, but your wrist rotates more along the outside bone. Now, your wrist can also shift from side to side. If you lay your hand flat on a surface and shift it side to side while keeping it flat, that's the motion I'm talking about.
Now, what this has to do with picking is, the position your hand is, from side to side, determines where in relation to your arm bones your wrist and pick are. The motion is centered between your two arm bones, slightly closer to the outside bone, so that is where your pick should be. So, the way to find the sweet spot is to just shift your wrist all the way to one side, and little by little move it back until you find the sweet spot. This means shift your wrist sideways, toward your pinky. If you turn your hand over, you'll see that the center of your pick is in line with the outside bone of your arm, maybe even past it. This is too far, but play for a moment just so you know how it feels. Then shift your wrist back just a littl bit. Every time you move down or up, the pick will move past the center of motion and back toward it. This is the sweet spot.
Note - whenever you shift your wrist, it changes the angle of the pick. So when you change the angle of your wrist, you'll need to change the angle that you hold your pick, in order to get the same angle. Hope this lesson helps.