I integrate it into keyword research.
For example, I have a vapor cigarette/e-cig client. It came time to optimize their "e-liquid" page. Knowing their a several variations of this keyword, I first found the keywords with the most volume.
After identifying the keywords with the most volume, I wanted to check how they were trending.
So I popped e-liquid, e-juice, vape juice, and etc in to Google Trends. As it turned out, "vape juice" was sky rocketing up and to the right in Google trends, thus I made sure that was one of the main keywords I was targeting.