When learning a language one must also deal with the somewhat arduous task of learning vocabulary and also actually remembering it! A key technique developed to help with the memorizing part is called spaced repetition.
Spaced Repetition is when a word or other item of data is repeatedly presented to the learner at varying intervals to help ensure that data is firmly and permanently imprinted in the brain.
An often used way to repeatedly present data to memorize is using flashcards and such a method does indeed work well, however it is not very scalable and memorizing a large amount of data with the old style printed flashcards can be rather cumbersome and is not really practical when you need to vary the intervals depending on the word or how easy or difficult you find remembering it. In this modern age there are of course better ways to do it.
Graduated Interval Recall is a type of spaced repetition developed for Pimsleur Courses. The popular audio based Pimsleur approach uses the following approximate intervals: 5 seconds, 25 seconds, 2 minutes, 10 minutes, 1 hour, 5 hours, 1 day, 5 days, 25 days, 4 months and 2 years although it is unlikely that anyone would still be listening to their audio files 2 years later.
Spaced Repetition is ideally suited to computer-assisted language learning and many such Spaced Repetition Systems (SRS) language programs and applications now exist to help with acquiring the vocabulary required to achieve communicative competence.
A number of useful and in many cases free SRS applications can be used to help provide repeated exposure of words or data at varying intervals. Examples of such software includes Anki, Gradint, Supermemo, Mnemosyne and others.
To use an SRS you simply load up a specific dataset for your language and the application will show you some new words to memorize along with previously learned words which you may have seen the day before or week, month or some other interval. Words which are easier to remember, as specified by you, will typically be shown less often while more difficult words are shown more frequently until they become easy for you to recall.
Depending on which language you are learning you can usually find many, often free, pre-made datasets of words (text, audio or even video) to load into your SRS of choice. If no such dataset exists to suit your needs you can also make your own and even then share your specific dataset with the wider language learning community.
A minor(ish) problem with some SRS programs is when you miss a day or two and the word reminders start piling up until you return and suddenly find yourself deluged in words, far too many to go through at one time.
These computer based spaced repetition tools are a great addition to any budding linguists arsenal and can often be run on many computer platforms such as windows, mac, linux, android etc. so you have no excuse to not fire up the SRS application any time you have a few spare minutes, wherever you are in the world!