Hand reading is not about superstition, but the disrepute of superstition has stuck to some extent. It's a commonly held belief that signs, shapes and symbols on the palm reveal significant events in the future, events which cannot be avoided. As a result hand readers are seen as some sort of psychics.
To start with, shapes of animals or things or even a shape like a circle has little meaning in hand reading, if such shapes exist at all. A pure trident (a line splitting upwards into three) is an uncommon sign, and when it is found it's usually the Sunline or the Fateline which has split at the end. The meaning depends on which line it is. A trident does not foretell an event and is not necessarily an indication of good fortune.
Stars and crosses have significance if properly formed, and not part of a main line. They can reveal some aspect of character, depending on where they are found. If found on or close to a main line (but not part of it), they can point to a type of past or future event (positive or negative), but there is no certainty of this event ever taking place. Lines disappear and new ones appear - along with changes in the person. The future event may not take place if the person changes his/her behaviour. What is fascinating is that lines indicating the past can also change if one's perception of the past changes.
Hand readers cannot predict the future with certainty because people's personalities do not remain static. It was easier to predict the future fifty or a hundred years ago when life held limited choices and there was some belief in fatalism. The lack of mobility, fewer career choices, less individualism and a reluctance to believe that the future can be changed meant that people changed less and their lives took predictable paths.
The fact is that a hand reader is as capable of reading the future as a medical doctor is! When a doctor tells a patient that he/she could die from cancer, the patient does not think of the doc as a psychic. People believe that they can improve their health if they change their lifestyle, and are often determined to prove the doc wrong. As long as actual changes are made (not dependence on stones, gems etc) life can improve. If the person believes that a tragic event is 'fated' to happen, and does not attempt to change, he/she could well meet his 'fate' sooner than he thinks.
You might also like: Can Palmistry predict future events? or Palmistry Explained or How to decipher signs and lines on a hand or Palmistry Myths and Misconceptions and how palmistry can help you lead a better life
Or What to expect from a private hand reading