Which things break the wudu?

I am confused over the fact that roaming in house where kids, mom or sister in law or sometimes guests in your boxers, can break your wudu? I am generally living alone, and mostly want to be comfortable while i am at home. so i prefer shorts or boxers.So sometimes my fiance shows up and i change later after i answered the door.
My question is, what sort of clothes in front of other break your wudu. And if smoking up a cigarette or non alcoholic beer like malt, breaks the wudu?