A conversation is a dialogue, not a monologue. That's why there are so few good conversations: due to scarcity, two intelligent talkers seldom meet. (Truman Capote)

You will find some really interesting information about the passive here. It is actually intended for teachers but I think you will find it well worth the read.
Have a look at the BBC's comments on the art of conversation. Then check out how to hesitate like a native English speaker and these hesitation strategies. Finally, what to do when stuck for words.