We have a pretty polyglot crowd here, so I'm hoping you have some useful suggestions. As many of you know, I am a native English speaker with a reasonable grasp of Hebrew. I took Hebrew classes throughout grade school and high school and have pretty good 'book learning' in the language, especially as you get to older texts. I have never been as comfortable with my conversational skills - I can get by in a social interaction in Hebrew, but get caught up by some vocabulary and grammatical problems on occasion. More importantly, I tend to express myself with a great deal of sophistication and specificity in English, so it really pains me to stumble along with a limited proficiency in Hebrew (this is also tied to the fact that this was always my worst class by a large margin - every other class was always an easy A, even classes that used Hebrew, but my Hebrew language classes actually required work to eke out an A-).
Due to a variety of reasons, my wife and I have chosen to raise our daughter speaking to her primarily in Hebrew. English is still the language of our household (i.e. how my wife and I speak to each other), and she picks up plenty of English and Spanish at school, but when we address her, it's mostly in Hebrew (we read books and sing songs in both Hebrew and English, though). This has borne fruit - most of the words she uses with us (other than some specific phrases) are in Hebrew, and she clearly understands the correspondence between the three languages (e.g. numbers, colors, nouns, etc.). I'm hopeful that the foundation we are laying will make her much more comfortable in the language when she is an adult, with a near-native fluency and comfort.
The only issue is that she is now starting to talk a lot more (she is two years old), and I can see the time looming when it is going to get a lot harder to keep up with her. It's easy to discuss our normal daily activities with her (generally revolving around toys, travel, food, sleep, and diapers), so I don't need to have a very sophisticated handle on the language and don't need to be able to discuss complex abstract thoughts. But I can see that sooner rather than later, she is going to need a lot more elaborate discussions - things like discussing feelings and appropriate behavior, and the questions that have increasingly complicated answers, etc. We have very specific opinions about how we, as parents, would like to handle these sorts of things, but they require a facility with Hebrew that I do not, currently, possess.
So, long story short: do you have any useful strategies to move from 'limited technical proficiency' in a language to a much more fluid and sophisticated handle on the language? I want to be able to discuss anything from science to philosophy in terms a child can understand (which, IMO, is almost harder than just learning how to do it with adults in a foreign language). Book learning isn't going to do it (though I have increased my consumption of modern Hebrew publications recently), and I rarely have the opportunity to converse in Hebrew with anyone other than my wife, who has similar handicaps (her conversational Hebrew is better but her book learning is atrocious). I feel like if we slip into English more and more, she will end up forgetting all of the Hebrew we've been teaching her - after all, we're already fighting a losing battle against school and American culture - but I don't want to compromise our other parenting priorities to I can teach her a stunted and simplified version of a foreign language.
What strategies have you used to improve your ability to converse at a high level in a second language?