Study another industry. This will help to show you how people outside your chosen field operate and give you ideas you can incorporate into your field. The industry could be completely different from yours, or have some overlap, but it should be different enough to give you a fresh perspective on your own
For example: the ad person might take a look at psychology topics or look into how the businesses they're asking for ads from operate.
The novelist might read outside their chosen field (YA) looking at nonfiction, mysteries, and the classics for inspiration.