Create a grid on your practice paper using a ruler and a pencil. First, determine how large you want your graph to be. For young children, begin with a large grid, like one divided into 1/2-inch blocks, with each uppercase letter filling two blocks tall, one block across. For adults, a smaller grid---similarly sized to standard wide- or college-ruled paper---will be more practical. Lightly pencil your desired grid size on the sheet of paper; don't mark too hard or it may, counter-productively, render your handwriting illegible.
Create reusable graph handwriting practice sheets by meticulously creating the grid using a pen, and then photocopying the sheet. For graphs with a smaller-sized grid, print numerous copies. For large grids, like those used for children, print one copy, laminate it, and let them practice handwriting using a thin dry-erase marker. (The tips of these markers are generally too thick to allow for effective practice on small grids.)
Practice your handwriting on the graph paper. Initial practice should focus on correctly completing each letter of the alphabet, both upper- and lower-case. Use the graph paper to regulate the size, slant and spacing of each letter---it is this regularity that will result in structured, easy-to-read handwriting. Once you have mastered the proper formation of individual letters, continue using the graph paper to copy passages and write sentences, focusing on the proper spacing and joining of letters and sentences.