Where might you start looking for trends?
You may identify a trend because you notice it organically in the world around you. You may also identify trends using media, both social and traditional, coverage. Often in-depth reporting will provide background of a trend or its development over time.
Here are a few sites you may want to use to explore trends. I don't recommend any of these sources above another, they are suggestions for a places to start.
Here are some questions to ask yourself: