Something can't really come from nothing. When you're brainstorming, it helps to have a starting point and a few rules to help you generate new ideas. Productivity and ideas blog the 99u suggests creating arbitrary constraints for those times when your brainstorming sessions need more focus.
Brain icon by Marcus Michaels (The Noun Project)
Enable creative thinking by embracing arbitrary constraints. What if your idea only worked between 2:13 p.m. and 2:15 p.m. each day? What if your mobile app could only show one sentence and one button at a time? "You're basically saying, look, you've got text, links, and 140 characters," says Will. "What can we do with that? It's normally a lot more than you think."
The 99u offers a few more tips for more effective brainstorming. Hit up the full post for additional ideas.
Never Brainstorm with a "Blank Slate" [The 99u]