I have a son who loves cars and trains, and this activity is great for such children. Tell your child that you are going to draw tracks for him to move his train on (or roads for a car). Then, encourage your child to move the car or train along the line you have drawn.
You can start with a simple track like a circle or a square.
Next, you can move on to patterns needed for writing like a zig-zag line.
Finally, you can draw alphabets and ask your child to move their train on it.
This is a great kinesthetic method to reinforce the shape of alphabets and the method of writing a letter. It is also good for children who are not confident with writing. Holding a car or a train is a lot less threatening than holding a pencil, and they also enjoy it.