well dreams are weird, sometimes I wake up, and have a feeling I had a lucid dream, in fact i KNEW i had a lucid dreams, but i just can't remember what i did, it's hard to explain. There really is not way to tell exactly when you become lucid, because the time is different.

to wake up from the LD, close your eyes or think about your body laying in bed. Yell "end dream" or something, or just let the dream fade away by doing random shtuff.