Think about it for a moment because a tidy mind makes for a happy student. You could have a notebook and keep it in a secure place and into which you add the name of each new essay topic whenever you come across it. You could have a file on your PC or tablet or even in your phone and add new essay topics to this file or folder whenever you think of them.
First of all they need to excite you. If you are not excited by the essay topic then the person reading what you've written won’t be excited either. Then it needs to be a topic which has lots of excellent and worthwhile research material. It needs to be a topic which lends itself to controversy. Here are some examples of good essay topics. As you read through them, consider whether or not they excite you, will have lots of available research resource material and whether or not they are controversial.
When you get to high school and certainly when you get to college you know that you are going to be asked to write a number of essays. In many cases the essay topic will be decided for you. You have no choice. But this is not the case all of the time. In a number of cases you will be asked to come up with the title and the topic of your essay.