Like @muppetish, I was taught to give up my seat for those more needing of it than my spry, unpregnated self. I was taught to respect the elderly and to try to help them if needed. I’ve carried grocery bags, helped steady an older lady as she walked down a rocky path, offered to let elderly people go ahead of me in line, that sort of thing. It just feels right, I mean, they’ve been around a lot longer than I have, not to mention they probably don’t have the same strength and stamina.
I’m exceedingly polite.. but that I think is just me (none of my parents or relatives taught me this.. some are outright rude to people). Working in the service industry, I know how hard it is to deal with people. I try to be one of the good customers. I treat all my waitstaff, counter people, etc. with full respect, a smile, and maybe a joke. I try to make their jobs easier.
I generally won’t pry into someone’s personal business. So, if someone mentions something, I don’t ask questions or pursue the topic. I figure if they want to talk about it, they will. I wonder sometimes if people take this the wrong way (i.e. disinterest), but it just seems respectful to me. (exemptions from the ‘no prying’ rule being people with whom I have long-standing, established relationships)
I’m sure there are several more.. I have a weird little code of conduct for myself that I live by. :P