There's a constant refrain in the Flying Maths Classroom, these days, of "I can't quite remember..." Whether it's a trig identity or $21 \div 7$, the outbreak of amnesia in the quiet suburbs of Weymouth seems close to epidemic proportions.
Well, one tutor can offer his students an experimental course of treatment to get these pesky facts to stick in their leaky memories. It's a treatment known as 'Anki therapy'.
I often advocate flash-cards as a way to remember anything you need to learn - be it maths facts, German vocabulary, or the capitals of sovereign states recognised by the UN. You get a big stack of cards; on one side, you write the question you want to memorise the answer to, and on the other, you write the answer. When you want to study, you try to answer each card in turn; if you get it right, you put it to one side, and if you get it wrong (or struggle with it), you put it to the back of the stack. When you've put all the cards to the side, you're done!
It's simple and effective - you have built-in repetition of the hard stuff without having to go through easy stuff over and over again - but there's one big disadvantage: you get to the station, your train is more delayed than it usually is and you think "I know! I'll run through the cards... which I've left at home. Candy Crush it is, then."
Anki solves that problem, unless you've left your phone at home. It's an online flashcard system (with LaTeX support, in case you're into that kind of thing) that automates the kind of spaced repetition putting cards to the back tries to - only it does it properly.
It shows you a question; you recall or guess the answer, and press the space bar to check it. You then choose whether it was easy, good or hard, and it gets scheduled for some future time accordingly.
While it's good practice to develop your own stack of cards for your own study needs, you can also get hold of shared decks from ankiweb.net, which other kind people have set up for you. (Or, more likely, for themselves and their students, but made available to everyone else.)
Like all study techniques, Anki is only going to work for you if you make it part of your routine and get into the habit of running through the cards every day or two - but once you do, you'll find that things that seemed impossible to remember suddenly start sticking.
* Thanks to Patrick for showing me Anki in the first place.