I recently spent a week at a countryside resort and the manager commented to me that I was the most polite foreigner he'd ever met, because I was aware of other people and didn't just care about myself. So I must be doing something right. Here are my observations....
Let's take as your starting point that you want to show your Asian colleagues and friends and the random people that you meet that you are intelligent, polite, and culturally aware but not to the point of slavishness and over-exaggeration. You want to fit in, not look ridiculous.
So.... yeah, tip one, don't bow too deeply. Don't bow at the same time you're shaking hands, that looks awkward. No-one is expecting you to bow at all, actually. You're a Westerner.
When we're bicycling through a Chinese village and we pass an elderly villager sitting in the sun, I do give them a smile and a head bob, to show respect. I hope they understand that I want to show respect for their grey hairs and for the fact that I'm cycling through their village. Or maybe I look like a dope. I hope not. Also when I'm called upon to speak in front of a group, I start with a little bow, because that is what all the other speakers do. It seems to be well received. Otherwise, I don't go around bowing at everybody...
The unspoken rules of physical contact are different here. I mean, if you are one of those people who routinely, even unthinkingly, hug people when greeting them, or playfully punch their upper arms, or pat their backs, be aware that you may startle a Chinese person by doing this, especially if you don't know them well. However, you'll observe many patterns of physical contact in China that you won't see in the West. Physical contact between friends is A-0K in China. Friends of the same sex, that is. Girls walk hand-in-hand, boys roughhouse with one another and are physically close in a way which would call down assumptions about their sexuality in the West.
Public boy-girl affection is frowned upon. Ross and I have drawn a lot of comment around the campus because we often hold hands when we walk. That's very unusual for an older married couple but people think we're cute and they tolerate us. French kissing would be a pretty shocking sight, however.
Some of my female friends and colleagues have tried to walk arm-in-arm with me. I enjoy that as much as Alice did. Also, when I've been walking over rough terrain in the country or in a crowd at a festival, my younger companions, out of respect for my age, have grabbed my arm and guided me along. It shows caring and affection for me, which is nice, even if it feels awkward.
On the other hand I have been love-bombed with hugs from swarms of little Chinese children that I've taught. Which is awesome.
Wait to be seated at a formal banquet. There is a definite pattern for banquet seating. Your hosts will let you know which seat is for you. Again, if you watch the Local Laowei series, you will be well prepared.
Don't talk loudly and don't gesture broadly when talking. The Chinese consider this to be vulgar. Actually, in the classroom, I'm a complete clown -- acting things out, making faces, singing, hamming it up. But in public, loud and brash "ugly American" style behavior is frowned upon.
Gentlemen offer to carry ladies' parcels and purse. You'll see young men carrying their girlfriend's purses for them and when I am with a younger female companion, they often insist on carrying my purse and my shopping for me. I enjoy this custom, especially when I have to haul books and a laptop around. Usually a student will step up and offer to carry it for me. This has more to do with my age than my gender, I think.
I think the most important thing to remember is that allowances will be made for you because you're a foreigner and if you keep your eyes open and watch how people interact with one another, you'll pick up the local unspoken etiquette rules pretty quickly. If making a good impression is important to you, I'm sure you will make a good impression. And we all know that, fairly or unfairly, we are ambassadors for our countries and our cultures when we're abroad.