It depends on your stance of the topic. Assuming that you're against texting and driving, you'd have to cite reasons and explanations. You need: an intro, 3 paragraphs stating reasons, (a counterargument if needed), and a conclusion.
You'd probably have to include sources and statistics, like the number of crashes or deaths annually, that are caused while texting. Also talk about the chemicals in the brain and waves in the phone, that increase distraction and slow reaction time.