Posture - Have your child check their sitting posture when at the table
Ideally the desk height should be 2" above their bent elbow when seated, their feet should be flat on the floor with their ankles, knees and hips all at 90° angles, their forearms are forward and stabilised on the desk and their back aligned against the back of the chair.
Try using a rhyme: "1, 2, 3, 4...Are my feet on the floor? 5, 6, 7, 8...Is my back nice & straight?
Paper - Have your child check the position of the paper
Encourage your child to tilt their page when writing so that the vertical side of the page is roughly parallel with the forearm of their writing hand.
Right-handed writers should have a slight angle, where as left-handed writers should have a steeper angle.
Encourage your child to use their other hand (“helper hand”) to hold the paper steady.
Pencil - Have your child check the way they're holding the pencil
The pencil grasp best for writing is called a dynamic tripod grasp where the pencil is held between the thumb and index finger and rests on the middle finger.
Right-handed writers should hold a pencil approximately ¾” - 1” from the tip; left-handed writers at least 1¼” from the tip of the pencil so that they can see the words they are writing.
If your child holds the pencil too high up, then consider letting them use pencils that are shorter, such as the size of a golf pencil.
Pressure - Have your child check the pressure they are applying when writing
Difficulties with pencil pressure may be because the child has poor tactile or proprioceptive awareness of the position and movement of their fingers or a weakness in their hand strength with poor control of the smaller muscles of the hand.
Consider the pencil being used. For example, a #1 Pencil has softer lead and requires less force to produce a darker result or a mechanical pencil helps a child control the amount of force they are using as the tips can break easily if too much pressure is used. You can also get novelty pens that are a great incentive as when the pen is pushed down with enough pressure, it either makes a noise or lights up.
Consider placing different materials under the paper or writing on different surfaces. For example, using a mouse pad or sandpaper underneath will encourage a child to use less pressure as when they press too hard they will poke holes in the paper; or using carbon paper underneath can encourage a child to press harder to make the writing appear on it as well.