I need more information to diagram the sentence "How do I diagram this sentence." To create a diagram, I need the specific type of sentence diagram you want (e.g., Reed-Kellogg, traditional, etc.) and the grammatical analysis of the sentence. The sentence is a question, containing an auxiliary verb ("do"), a pronoun subject ("I"), and a verb phrase ("diagram this sentence"). "This sentence" is the direct object of "diagram." "How" functions as an adverb modifying the verb phrase.

To generate a diagram, please specify the diagramming method you prefer. Then, I can provide a detailed, step-by-step construction of the diagram. For example, a Reed-Kellogg diagram would show the sentence's main clause and the relationships between its parts using lines and branches. A traditional diagram might use a more linear approach, showing the subject, verb, and object in a specific order.