Let's start with the most important one; not all Parisian's are rude. Yes, they're not too fond of tourists, and they may answer back in English if your French isn't up to par. However that's not just because they can't be bothered, sometimes it's because they want to help you. But you'll get an A for effort for at least trying. My suggestion to fix the issue is to stay away from touristic places. If you only have a couple of days to spend here, other than the occasional museum visit, try to go to places where you don't have the chance of running in to your best friend from back home.
The cabs are expensive. Especially when you want to get home after a couple of "du vin," but the metro is easy to master. I won't lie, I did get lost my first time and was underground for longer than I wished for, however that was the first and last time. So use the metro. Yes you don't see the city, however getting stuck in traffic by the Seine isn't as chic as you might think.
When travelling in Paris, it's not like travelling in, say, New York. Leave your sneakers at home. Find another pair of comfortable clothes. Running around in stiletto's are hard on vacation, that's understandable, however there are shoes that look good that don't resemble what you wear to the gym. And when in doubt, wear black.
Meals are the best part of your day. Most Parisian's take lunch at 1 and go back to the office no earlier than 3. Now I don't know how this works, but I can easily see a Parisian putting that in their contracts. So slow down, take your time. I promise you this; no one is going to rush you through your meal. You can eat, and drink, and eat, and drink some more. (Salad, wine, desert, more wine.) Take a book with you, or a magazine. Or just sit down and watch the people; it's impossible not to get inspired.
The food is as good as "they" say. So don't come here for a few days with a diet in mind. One taste of that butter, you're done for the week. And if you don't have mille feuille with freshly made creme and strawberries, then you're missing out.
Arrondissement 7 & 8 & 9 aren't the only areas to hang out in Paris. Try the Marais on a Sunday. It's the only place where you'll find cheap vintage, open boutiques, and a relaxed crowd all in the same place. Or go for a picnic at Jardin du Luxembourg. Even better, go to the Shakespeare and Company book store at the 5th arrondissement.
Last but not least, for the love of whomever-you-believe-in, bring a scarf. It's a sin not to wear one.
all pictures via tumblr.