What percentage of our brains capacity do we (humans) actually use? Would we be able to use more if we tried? How?
The idea that we only use a small proportion of our brains, often quoted as ten percent, is unfortunately a myth. In fact all of the different regions of the brain have a function and even simple actions require the use of many different regions.
The most likely route to increased brain capacity is through technology. Scientists are already capable of linking brain function to technology, for example to assist people that have spinal injuries with communication or motion.
The next steps may still be a distance away, but eventually we will download skills, abilities and knowledge direct to our brains in the same way we currently download applications to our phones.
Of course, there are considerable ethical concerns with such technology. And hacking becomes a really serious issue.
Until then, we are all just going to have to study!