Spaced repetition is a simple study principle: I show you the front side of a flash card bearing, say, a word in Spanish. You then have to tell me what that word is, in English. If you got it right and it was very easy, I won't ask you again in another two weeks; if it wasn't so easy, I'll ask again in a week; and if it was really hard, I'll ask again tomorrow. In this way, you don't have to spend time going over material you already know–the system adapts to the data you've acquired, Software like Anki (free and open-source) bring ease, sophistication, and much more power into this process. And if you think flash cards are only for memorizing trivia or language, you'd be surprised.

Trivia and language are the two most common uses, and flash cards are great at that. I first tried using Anki almost two years ago, when I decided to master the NATO phonetic alphabet (Alpha, Beta, Charlie, and so on). I used Anki's mobile companion, AnkiDroid, for most of my studying, and it was remarkably effective. Within a few short days I was able to spell out anything using the NATO alphabet, and I retained the knowledge for months. Recently, I came across something called the Janki Method, in which you use spaced repetition to learn anything, including computer programming, and not just limited sets of data.

The key piece here is creating your own decks of cards. Anki plugs into a free service called AnkiWeb, which hosts many ready-made shared card decks. There are some users who carefully created extensive decks of cards for learning anything from anatomy to Japanese, and it is very easy to download these packs. Creating one from scratch seemed like a lot of work, until I realized the key was to do it incrementally, one new datum at a time, as I learn.

Anki makes it very easy to create new cards, and you can create different types of cards. The most basic type is the traditional flash card. There's also a reverse card, where you're sometimes shown the front ("Chair") and sometimes the back ("Silla," Spanish for chair). You only enter the information once, and Anki is smart enough to generate multiple cards based on the data.

Another great type of card is the Cloze, where you include a paragraph of text and blank out some words ("O say can you see [...] early light"). Anki then shows you the card and you need to recall the missing part. You can also use one block of text to generate many Cloze-type cards, making card generation very easy.

You can also have Anki prompt you to type in the right answer using your keyboard, which is excellent for mastering programming language syntax. There is an art to creating the right type of cards: SuperMemo, a commercial spaced repetition product that preceded Anki, put together a great list of the 20 rules of formulating knowledge in learning.

Anki is a mature product, but its interface can seem unintuitive at first. There is a learning curve to both the system and Anki, so if you're just starting out, you should probably find a ready-made pack of cards and use that for a while. You can then transition over to creating your own cards.

All in all, if you enjoy learning new things (or have to, for school), Anki is an invaluable piece of software, well worth the time it takes to master and use on a daily basis.

Note: The Download button on the Product Information page will download the software to your system. This program is a known to receive false positive malware results from Norton Antivirus.