I had great success learning vocabulary using the Leitner system. It enables you to add new words on a daily basis (from 10 to 250 depending on the effort you put in) while keeping the need for repetition at a minimum. This is achieved by a special method to sort the cards depending on how well you already know them. A typical card index in the Leitner system has 5 different boxes. The specialty of such a card index is however that not all boxes are of the same size. The length of the boxes increases exponentially.
Now to learn a word you write the English word on the front of a card and the translation on the other side. If you have enough cards to fill the first box you can start. If you know a word you can put its card in the next box, else put it at the end of the first box. With time the second box will become full. With the cards from the second box you pretty much do the same thing However there is one important difference! Cards you didn't know won't stay in box 2 they go straight back to box 1. So basically if you know a word its card goes in the next box, elsewise it goes back to box one.
This way you will only be frequently repeating words you don't know well yet, enabling you to learn them better, while repetitions of words you already know very well are kept to a minimum. If for example you learn a word at the first time you see it you will only have to repeat it 4 more times.
You can use the following sizes for the boxes:
1: 1 cm
2: 2 cm
3: 4 cm
4: 8 cm
5: 16 cm
A card index for the Leitner system could look like this:
