how I learn spanish

My Spanish is generally learned by need. So I get a lot of holes in it. For instance I can say:

Why are you bothering her? - Estas fastidiando la?

Why are you flirting with her? - Estas coqueteando con ella?

This is not boring. - No esta aburrindo. (sp?)

I check all my spanish past three speakers. I make sure that it is "polite." "Can you say this to your grandmother?" I make sure that it is appropriate for an adult to say to a teenager.

Despite all this I *frequently* find out that I have missed something.

Today I learned that "chilango," which I thought was merely a nickname for those from Mexico City, is actually used for pickpocket...still a nickname for someone from Mexico City. I had been assured that it was polite and simply a nickname. I learned this when mijo snatched my nectarine off my desk at lunch and then asked me did I want a "peach." (I forgave him for not knowing the difference. Pretty impressed he knew the word for peach!) My teacher friend turned to him and said, "You little chilango!" When I inquired, really out of curiosity, why people always say that to the D.F. kids and tease them about taking stuff she filled me in that "chilango" has the connotation of pickpocket.

So there you go...why it is dangerous to learn languages by immersion. :)