I have wrestled with this question as well, and there was a time I didn't even know how to articulate the question (which itself exhibits the problem).
The problem: You can read and hear words and understand what they mean, but when you need to formulate your own sentence, the words aren't available to you. They may be on the tip of your tongue (if you're lucky); or they may be absent.
I could read and listen and I knew the meaning of the words I perceived. I could do very well on verbal tests--especially multiple choice.
Another way to phrase this problem of active versus passive vocabulary comes from the field of memory.
The difference is between "recollection" and "recall," (I hope I'm not confusing the two terms or even misremembering one of them--that would be unhelpful).
The idea is that there is a clear difference between, say, a multiple choice quiz which provides you with a choice of 4 provided answers; and a quiz that demands you to come up with the correct answer yourself--either by writing it in the empty box or saying it.
If you intend to give a speech, then recognition will not help you. You need to recall, not recognize. Giving a speech is a very active activity, and requires you to recall; whereas listening to someone give a speech is more passive, and requires you merely to recognize (or understand the input).
I have found that I can perform well in recognition tests, but I often can barely formulate a coherent sentence when I'm anxious or I've not communicated for a day or so.
Here are specific thingamabobs which I've noticed help me:
1. Reading any well-written passage, OUT LOUD. I've used <PERSON>, an English translation of <PERSON>, and <PERSON>. You might think that <PERSON> would not be very helpful, since his writing is filled with archaic, obscure words and may seem clunky--but reading it out loud seems to have a magical quality of dramatically improving my active vocabulary.
2. Reading any well-written passage, out loud IN YOUR MIND. This has the same effect as #1, but you must HEAR a voice--any voice--in your mind as you read the words. To be honest, I have no idea how this works, but it does. 873
When I used to speed-read, I read silently and fast. But I stopped speed-reading on purpose because I noticed it seemed to relieve me of my active vocabulary. Words were not easily accessible anymore. I deliberately read books out loud, or heard a voice in my mind read it. In fact, this impaired my comprehension during the reading, but it greatly improved my active vocabulary and sentence structure while talking.
3. Reading the dictionary. Unfortunately, it is hard to find an electronic dictionary you can read cover to cover. You may need a paper one for this exercise. I still have yet to find an online or e-book version of a dictionary which you can read from A to Z. I have not even read beyond the letter B, but I have found that reading the dictionary indiscriminately always helps my active vocabulary (even beyond the letter I'm on). It sounds boring, but it is a good exercise. 312