Bad habits are difficult to correct if they have been practised from the start. Teach large arm movements initially, setting up a rhythm. See that the whole body is balanced either when sitting or when standing. If he finds these hard, check that he looks to see where he is going next rather than letting him jump off into space. Similarly practise drawing paths through mazes etc.
Activities encouraging gripping and fine manipulation are essential.
If there are problems get the child to talk his way through. If your child has a learning difficulty, these points will help him to link hand movements with what he hears, with what he sees, with what he says and with what he understands. Hints to help reading Reading stories, picture books and fairy tales should be a fun experience for both you and your child. To begin with, get cosy so that it is a warm loving situation. Start with picture books and just talk generally about what is happening.