List any topics that arouse your passions. If you like sports or dancing, these might be topics that you can write about easily.
List the topics that you are knowledgeable about. You will find writing your essay easier if you write about a topic that you already know something about.
Think about the topics you are considering. How involved can you get in the topic? It is important that you can research the topic you decide to write about.
Make it interesting. A boring topic makes for a boring essay and even your teacher doesn't want to read boring essays. Choose a topic that your peers haven't already done. Biographies of famous celebrities are overdone, but if you choose a specific aspect of the celebrity's life, then your essay may be more interesting to your readers.
Trim the topic down into ever smaller categories. For example, take the topic of celebrity and make it specific: Celebrity = Michael Jackson = Neverland Ranch = parties at Neverland.
Use prewriting techniques, including freewriting, listing or clustering. When you freewrite you just let your mind focus on a particular subject, and then you write everything you know about it. Listing and clustering is freewriting in list form or in a cluster.