If you've written a speech before, you're probably familiar with making an outline, taking notes and organizing your materials. If you haven't, here are a few things you can do to make it easier on yourself: start by writing out each step or item that your teacher's instructions mention. If you know exactly what your teacher wants, that will help in laying out the foundation. Now you can write a brief summary of what each part of your speech should look like.
Next, if you haven't been given a topic or haven't chosen one already, you need to pick one. Make it something that you're interested in at least a little, because if you're bored by it, your audience will be too. If you were given a topic and you hate it, try to find some part of it that inspires you. During your research, look into every avenue possible related to your main topic that you can exploit for ideas. You'll eventually find something you like even a little bit to talk about.