The first step in teaching the written form of numbers is to use the Montessori Sandpaper Numbers.  I bought a set here that I like because they show the direction the child should move her finger.

This work is similar in concept to the Sandpaper Letters.  You lay out the cards and trace each number, saying, “This says 1.  This says 2.  This says 3.”  I start with just 1 to 3.  Once those are mastered, I’ll add 4 and 5.  As with the Sandpaper Letters, L has mastered the second period, so now we are working on the third.

Tracing the sandpaper is a precursor to writing.  The rough sandpaper helps reinforce the shape of the number, and tracing it is practice for making the correct movements to write the number before writing has been mastered.  Sandpaper Numbers also work on number recognition and number as a symbol.  The next step is to add numbers as quantity — I’ll post about that soon.