Repetition, repetition, repetition. That's why full immersion works for language acquisition. When you are fully immersed in another culture, you have no other option but to use what you know, over and over again. With time, more knowledge gets added, but it's the simple fact that you are practicing so much, repeating the same errors and correcting them, using the same vocabulary, that allows you to learn at a much faster rate. If you're unable to fully immerse, you must try to replicate that where you are, as much as possible. Use the new vocabulary repeatedly and eventually it will stick.