One of the best ways to solve a problem is to walk away from it. Change the environment in which you're attempting to solve the problem. Give your brain space to think outside the narrow focus you've occupied.
Take a breath.
Whenever you take a deep breath in through your nose and out through your mouth, it's a refresher for you brain. It gets the juices flowing again — or can calm you down if the problem is a source of stress.
Take a walk.
I love taking a walk to think through a problem. It gives my brain time and space to breath. And it forces me to exercise and get the creative juices flowing. I can't tell you how many times a walk has given me just the solution or realization I needed.
Sleep on it.
There is science behind "sleeping on it" because our brains continue to think through the problem while we sleep. Now if that isn't the most efficient thing you can do, I don't know what is.