“Get out. I need to go to my mind palace.”
Part of the reason Sherlock solves cases so well is that he can remember everything he’s ever seen or heard about (well, everything he deems important, which does not include basic astronomy). As revealed in “The Hounds of Baskerville,” where the above quote comes from, he does this by creating a “mind palace,” an imaginary place where he stores all the relevant images.
Apparently, this is based on a real memory technique that some people use. Here is a handy step-by-step guide to the process. I have not tried this myself, so I don’t know how well it works for the average person, but it sounds rather clever. We can’t all be as observant as the Great Detective, but perhaps this is one way we can bring our retentive powers a little closer to his.
And here is another article in which some university students describe how they use this technique to help with their school work. Cool, yes?