The main things to keep in mind when writing any speech are your audience, subject and purpose. Since your purpose is motivational, that leaves audience and subject. I will assume that the audience is your class.
A motivational speech can have a specific subject other than just general motivation. For example, if you are talking to the football team, you might be trying to convince them to win a big game. I suggest you choose a specific subject for your class. For example, you might try to motivate them to do well on an upcoming test, or to choose a specific career based on something they are passionate about.
Let’s talk about organizing your speech. The organization of your speech is very important. In a motivational speech, you want to start out strong. I suggest a motivational quote. Choose something that speaks to you without being too cliché. I like this one.
"Take up one idea. Make that one idea your life--think of it, dream of it, live on that idea. Let the brain, muscles, nerves, every part of your body, be full of that idea, and just leave every other idea alone. This is the way to success."
You need to introduce the quote. You should begin with the speaker. For example, “Swami Vivekananda, an Indian Hindu monk, once said, .… Once you are done with the quote, you need to jump right into the speech. Your speech needs a clear thesis, like any other type of writing. Have a message. Your message might be something like this.
If you have a passion in life, you should use it to choose the right university.
That is just an example. You connect it to the hook, which was about the importance of an idea. Then you will build your motivational speech around this principle. You need to have clear ideas for your speech. I like to use the rule of three. Basically, this means three clear ideas.
Throughout your speech, you can continue the idea of using quotations from experts or inspirational quotations. If used correctly, this will make your speech emotional and catchy. It is best to make sure these quotes are short and there are not too many, and they are spaced appropriately.
Do not forget to end strong, like you started strong. You can end with a quote too, as long as you have not used too many. You do not want to over-use the quotes. However, ending with a quote can be powerful. You can also just remind the audience of the quote you used to start with.
Make sure that your speech keeps to the time limit. There is nothing worse than a speech that gets cut off so that you do not get to say everything you meant to say.
Think about your class, and what motivates them. What do they need? What is meaningful to them? Do not forget about your delivery. Part of the motivating factor is in the writing, but part of it is in how the speech is delivered. You need to be energetic, and modulate your voice. Use gestures, inflection (emphasis of voice), and movement. Have energy and passion for your subject! Show them that you care about them and what you are talking about, and they will care too.