1. Hand should be around the size of the face
2. 5 fingers is always better than four (ik it can be a style choice, but I'm sorta copying other peoples advice)
3. The thumb is the largest and shortest finger, placed lower on the hand. The pointer finger is shorter than the middle finger, the ring finger is slightly taller or shorter (depends on the person) and the pinky is the shortest, next to the thumb.
4. Use your own hand as reference! :)