Choose a topic that genuinely interests you
When choosing a topic for your speech, you must consider your interests. For instance, if you have no interest in politics, you would not be able to deliver a good speech about current affairs. The topic of your speech must come naturally to you; only then will you be able to make an impression on the audience. A smooth and natural flow is one of the most important things that needs to be kept in mind when writing and delivering a speech, and this will only come to you when you are deeply interested in the topic; genuine feeling will show, and the words will come straight from your heart.
Read the newspapers
If you are unsure about what the topic of your speech should be, and the event at which you will be delivering it is just around the corner, you should start reading the newspapers regularly. By skimming through the latest news and/or the editorial pages of newspapers, you will definitely be able to fix upon a good topic for your speech.
The topic should be relevant
If the topic of your speech is not relevant to the event or audience you are addressing, you will fail to make any sort of impact. Therefore, choose a topic which is relevant and has a direct effect on the lives of the people in your community.
The topic should be current
You should give preference to topics which are related to the current scenario in the world, and are affecting people all across the world (or at least in your region). For example, when delivering a speech in the United States of America, you cannot discuss the problems of South Asia, unless they are relevant to the people of the US in one way or another.
Think outside the box
It is recommended that you put a good amount of effort into selecting a topic that is different from the run-of-the-mill topics most orators tend to go for. Think outside the box, but do not select anything too elaborate or obscure, and make sure you consult someone learned and experienced before finalising your topic.