My two favourite methods are Cinderella and the Voice Recorder.
The Cinderella is the old “little pieces of paper” method, with a twist.
1. Buy a thicker kind of paper or recycle a piece of cardboard that is blank on both sides.
2. Cut it up into small straps, more or less 1cm by 5cm.
3. Write your word or expression in English on one side of a piece of paper (I prefer expressions or words with their collocations such as prepositions)
4. Write its translation on the other side but remember:
a) use a pen of a different colour
b) turn the piece of paper upside down and not like a page in a book (this is how we turn little pieces of paper in our fingers, it´s more natural)
c) don´t translate word for word, choose a natural-sounding translation
5. Continue until all 30 odd straps are filled up
6. Wait at least a few hours before revising – right now you remember the words because you have just used them.
7. Keep your pieces of paper in a matchbox or a tiny purse.
8. To start the revision, turn all your pieces of paper the same face up (if you have used the same colour for the English version, you don´t have to read each piece to turn it correctly).
9. Remember that it´s more difficult to translate from your language into English – and so it´s the recommended method.
10. Choose a piece of paper and translate its content. If you remember it well, put it on pile one. If you don’t remember it well, read the translation on the other side, then put your piece of paper under all the pieces of paper you haven´t read yet.
11. In this way, you revise until you remember everything.
12. In a little purse, instead of two piles you can have two compartments.
This method is good when you are for waiting for something. However, if you spend a lot of time walking, consider recording expressions and their translations using your mobile or a voice recorder. Remember to leave a long pause between an expression and its translation. You could also repeat the translation after another pause.
If you don´t have enough time, just use http://quizlet.com/