My way to enrich the vocabulary of English is so:
I am searching in the dictionary for example names of animals, I am repeating them - and then on the the sheet I am writing out from the memory the most names of animals, as many I will remember. The same I am dealing with names of plants, of colours etc.
The other my way is very simple: I am making the list of English words and their equivalents in my language (Polish). Then I am covering the English part and I am writing out English words, I am checking - and this way to the effect, as far as I will write out all English words correctly.
Presumably these are trivial methods, but for me it works. :)