Have you heard of Anki? In this program you enter the vocabulary you want to learn (include pictures, ... - makes it easier to remember the words, plus it makes learning a lot more fun :) ), revise these words regulary (the programm tells you when to learn what) and then they stick much easier. Of course, it needs some work to enter all of the words you want to learn, but it is really worth the effort :)

What I do is make a recording in my target language of a story that is relevant to my life.   The story is only a couple of minutes long, but I record the same story over and over for about 20-minutes.  Then I play the recording in my car while I am driving. 

I listen to the recording maybe twenty times.

I agree with Anastasia, Use the language daily. You learn a language (and also reinforce grammar you`ve already learned)  by hearing the language spoken and speaking it yourself. That makes you remember new vocabulary. The use-it-or-lose-it-rule applies no better then with language learning.

I agree with Anastasia. Be active. That's it:)