Watching previous commencement speeches online, writing down the main messages you want to convey, adding humor when possible and being self-depreciating in tone all help you craft a graduation speech that is both heart-felt and entertaining to listen to. Decide what you want your main message to be first, and then keep re-writing your speech until everything you say is helping to express that message.
Think of personal stories that are meaningful to you, as well as inspirational quotes that have special meaning to you and help convey the message you want to focus on. However, make sure the speech is not just about you, and try to focus on ideas and messages that apply to everyone in your audience. Brainstorm by writing all of your ideas for the speech down on paper. You can then start crafting the speech together by eliminating the ideas that do not help your message.
Read your speech aloud once you have a draft written, and time yourself to determine how long the speech takes. This helps you decide if you need to trim the speech down or add more to it. Perform drafts of it in front of loved ones to help you with your delivery. This process also helps you correct any awkward phrasing, and it can affect the order of your topics. Keep practicing it as graduation gets closer, so that you are fully comfortable with the material and are confidant in your content before you take the stage.