Practice fine motor skills before starting actual writing lessons. Children with autism often have weak motor skills, so the earlier you can start using activities to improve gross and fine motor skills, the better. Fine motor skills are necessary in order to hold a pen or pencil correctly, and to press hard enough for the writing to be legible.
Some good activities for developing fine motor skills are playing with clay, sand or other squishy objects; picking up and sorting dried beans or pasta; coloring or painting and lacing activities, such as cards with holes punched in the outline of a picture or letter so the child can lace yarn or shoelaces through the holes.
Show the child how to trace outlines with a crayon or jumbo pencil. If the child is having trouble with finger strength and motor skills, let her use markers or a paintbrush so she doesn't have to press as hard. Difficulty pressing hard enough for people to clearly see the writing can be caused by poor finger strength, poor fine motor skills and coordination. It also can be caused by sensory issues, where the child has trouble receiving input from the outside environment and processing that input. With sensory integration problems, the child may actually have trouble with knowing how hard or soft he is pressing on the paper. Tracing pictures, letters and numbers and connecting the dots are all good practice.
Provide the child with unlined writing paper and have him practice making straight lines, shapes and circles. He should always start at the top of the line, moving the pencil downward, and at the two o'clock position of the circle, moving the pencil counter-clockwise, as in writing the letter C. Insist that the child holds the writing implement in the correct position for writing properly later on, and forms all parts of the shape in the traditional order for writing a letter: "Every line should be drawn left to right or top to bottom. Vertical lines are drawn first, left side, then right side, and then the connecting horizontal lines. The horizontal lines on top are first, and all horizontal lines should begin at the left. Kids have their own short cuts, so these basics do need to be taught," according to Stout.
Draw boxes for the child to put the letters into, one letter per box; this works well for the most concrete learners. Each box should be just big enough for the letter to fit, starting with somewhat larger boxes until the child develops more skill. Give the child a page of properly written letters to begin copying into the boxes. Many children prefer learning the letters to write their own names first.
Try the handwriting paper that has raised lines that the child can feel with her fingers and through the pencil, as the child masters writing letters in the boxes. Autistic children are visual learners, and so the typical wide-ruled paper may not be enough support to help them learn to stay within the lines.
Switch to the traditional wide-ruled handwriting paper once the child is doing well at making properly formed, consistently sized letters.
There are many inexpensive workbooks that divide the letters of the alphabet into similar groups, showing the child the letter to copy, as well as arrows to show which direction to make each line. These directions may be lost on an autistic child, but will still help you to determine how to teach the letter formation, as well as the grouping of similar letters.