Draw a straight, horizontal line on a piece of paper using your ruler or straight edge. Press lightly with the pencil so the line is visible, but not too dark.
Draw an identical line a distance below the first. The distance between the lines depends on how large you want the letters. The ruler works well because it allows you to measure the exact distance as opposed to just eyeballing it.
Draw a dotted line directly in the center of the first two. Use the same pencil pressure to ensure the line is as light as the others. If you have the ruler, you can make an exact measurement. If not, just line it up as best you can. This line serves as the midpoint for each letter. For example, the middle part of the letter "E" corresponds with the dotted lines.
Repeat Steps 1 through 3 at equidistant intervals below until you have a complete page of penmanship lines.