Almost every man in china smokes tobacco (unlike in Australia where it is mainly a young women's pursuit). There are no regulations governing smoking in enclosed public spaces. So get used to it. Buses, taxis (the driver), restaurants, EVERYWHERE, you will find cigarette smoke to satisfy even the most compulsive passive smoker.
No use asking them not to smoke ("qing, bu chou yan") as it will be seen as rudeness on your part, and will be ignored.
Like spitting and urinating in public, it is just part of the charm of the chinese male. Get used to it, and take lots of photos to gross out your friends...
People love babies. If you are not a tourist somuch as a resident, and take your family with you, you will find people here will gush and drool over your "foreign baby" (waiguode baobei).
He or she will be patted, grasped, kissed and generally wiped upon by a multitude of germ-carrying middle-aged women, with no thought of asking first.
If the spread of disease to your offspring worries you, be on your guard. These women move quickly and can be upon you and gone again before you even realise.