If you have a topic, be sure to learn how to restrict your topic. Your topic should be specific. If you have broad topic, you will have to cut it down to manageable proportions. Always limit your topic into specific one.
For example your topic is all about traffic. It is a huge problem and you will not want to deal with the problem entirely. Instead, choose the part of the problem that you can write about with some confidence. All topics can be viewed from different angles and this one, too, can be subdivided into several minor aspects, any one of which can become a topic for a paragraph. Like for example: (1) describe what streets looks like at peak hours; (2) show how a traffic jam forms at an intersections; (3) focus on possible causes of the problem on the street in front of your school and; (4) narrate an incident caused by driver behavior; and so on.
If you have topic about television shows, you can cut it into several topics such as noontime shows, noontime shows on Channel 5 or Sunday noontime shows on channel 2.