Make children write school lessons repeatedly to improve handwriting. It is difficult to keep children sitting in one place for an hour. It is better to buy colored pencils and pens so that they can practice writing regularly.
Their attraction to pens is what drives them to write more. Fountain pens, especially those with blue ink, help children write easily without putting pressure on their fingers. Children can get used to writing with such pens.
Teach children to write by holding the pen and pencil at the correct angle. Many children write lying down and leaning to one side, which affects their handwriting. When you sit on a table and chair and hold the pen properly, the spine will be straight and the writing will be beautiful.
Children should always read and write in the light. Do not read or write in low light. It also affects their vision.
For children with small hands, you can buy small pencils and pens specially sold for children. Thus they will not be bothered by the weight and size of the pen. 
It is wrong to force left-handed children to write with their right hand. Parents should realize that this will greatly affect their handwriting.
Children can be made to write with sketch, gel, zigina pens. This will make them interested in writing. You can show them YouTube videos on how to improve handwriting on your smartphones. Thus they learn and master many things through video.