Dr John Medina has applied recent developments in neuroscience to come up with a twelve-point plan for maximising brainpower. You can give your brain a workout over at his web site, Brain Rules.
Some of the ideas may be surprising but are founded in science. Rule 1 suggests that our brains will work better when we are walking. The reason is evolutionary. Humans walk and have walked over vast areas of the globe and our brains developed on the move. So going for a walk to mull over a problem is probably a good idea. Sleep is the subject of rule 7. NASA pilots found they could concentrate better after a 26-minute nap and other research backs up the brain organising benefits of good sleep and the occasional nap.
Next time you are having problems gathering your thoughts or making a decision, have a look through the 12 brain rules and see if there is a way forward for you there.