My husband and I went to Paris for 5 days last year. It's no different than any other large city. People have places to go and things to do so they aren't going to stop and introduce themselves. They ain't got no time for dat! The best advice I found was that the French are actually a very formal society. Don't just start asking, "Where is the closest train station?" That comes off as being rude. The equivalent would be if someone from Spain came up to you and immediately started talking to you in Spanish. Start with, "Bon jour. Excusez moi, Parlez vous anglais?" It also seems like Americans are much louder than Parisians. I can see how that could be annoying to people who aren't used to it. Your closest allies will be other American tourists. I feel like there's an unspoken fraternity when I meet other Americans overseas. There definitely is a coldness that Parians exude, but whatevs, I'm doing me so who cares?
Dress: Most Europeans dress much better than Americans. We wear shorts, t-shirts, and tennis shoes. They put much more effort into what they wear. European women traverse streets like nobody's business in some heels. Me, I don't walk as much as I do on vacation, so I'm okay with wearing tennis shoes and sticking out. I think they wear so much dark colors bc it's more of a apartment based society, so washing clothes isn't always the easiest.
TripAdvisor has a good forum for advice.
We really enjoyed the Underground Street Art Tour. You'll get to walk around neighborhoods. In our case, we got to interact with 3 different English-speaking Parisians (2 ex-pats) who were able to give us details on what it is like to live in Paris.
I always do an Open Bus Tour on Day 1 when visiting cities overseas so I can get the lay of the land and check out line lengths.
[Verjus / Verjus Bar](verjusparis.com/en-main/) - Delish food by some American ex-pats. The husband works upstairs with Verjus and the wife works downstairs in the bar. If I remember correctly, they are from Minnesota. The bar has amazing and more affordable food. Just because the wife's English is impeccable, don't let that fool you, she has the Parisian coldness down pat.
BATHROOMS: I didn't have a bad bathroom experience, but that's partially because I couldn't find many.