Some good tips for improving handwriting include holding the pen correctly, slowing down and using the shoulder more. However, the most effective methods depend largely on an individual's writing habits.
For example, many writers find themselves pressing down very hard onto the paper. This causes fatigue and prevents writing from appearing smooth and effortless. A large part of the problem is having the wrong grip on the pen or pencil. The grasp should be light but still supportive so that writing does not appear stilted nor too light and uncontrolled.
Writing slower can also be beneficial, allowing the writer to pay more attention to the appearance of each letter. Writing with the shoulder instead of the fingers or wrist can reduce fatigue and muscle cramps and allows writing to flow naturally.