Draw a horizontal line that is long enough to write at least two words. Draw a vertical line through the center of the horizontal line to divide it in half.
Find the verb in the sentence. For example, in the sentence "The laughing boy ran fast," the verb is "ran. Write the verb -- in this case "ran" -- on the line to the right of the vertical line.
Locate the subject of the sentence. The subject is what the sentence is about. In a simple sentence it is a noun that occurs before the verb. The subject of the example sentence is "boy." Write the subject to the left of the vertical line.
Check the sentence for articles. Articles -- either definite (the) or indefinite (a or an) -- precede nouns. If there is an article, write it on a diagonal line connected to the horizontal line under the subject.
Write the base word of the participle on another diagonal line under the subject, to the right of the diagonal line that holds the article. In the example sentence, the base word of the particle "laughing" is the verb "laugh." Finish diagramming the participle by writing the suffix -- in this case "ing" -- on a short horizontal line extending to the right from the bottom of the diagonal line holding the base word.