I've only been here two months but here are my take on things.

Hoan Kiem/Old Quarter = kind of the college, post college drinking area. Backpackers, cheap hotels, cheap beer, souvenirs etc. Seems like the most fun to live in.

Westlake/Tay Ho = the 30-40's area, more upscale, better restaurants, foreign restaurants. Quieter neighborhood better set for couples and families without children.

Ba Dinh = The political district, mostly locals, very quiet. Most likely where everyone works who isn't a teacher.

Ciputra(spellings probably off) = never been here, but its supposed to be the city that can be anywhere. Built like a western suburb, you don't really need to leave the confines of the area to survive, other than for work. Wealthy expats that work in Hanoi can be found here.

As for getting scammed, ripped off. Unless you consider getting charged 6k(roughly .30c) dong instead of 2k(roughly .10c) dong for watching your motorbike, I haven't seen any instances of scamming/petty theft.

The differences among neighborhoods in Hanoi are not as markedly different as in the US or some other countries. After all, we are a very homogeneous people in the cities (the 64 ethnic groups account for less than 10% of the population and we only see them when we travel). We also speak in the same way (with different accents of course) whereas in certain countries rich people will speak in a certain way and poor people also have their own way of speaking.

That said, there are mild generalizations that can be made about the districts in Hanoi

Tay Ho: Nouveau riche Vietnamese, expats, big villas, fancy restaurants, coffees that cost 7 times more than other parts of Hanoi, gated ahem prison aka Ciputra, UNIS brats, soon-to-be-the-new-home-of-the-largest-mall-in-Vietnam.

Hoan Kiem: Very commercial oriented but also the best part of Hanoi. It never floods here. Also, the real Hanoians (I'm talking several generations) live in the Old quarter. Very few outsiders bought a house or started up business here owing to the exorbitant property prices in this district. Wouldn't call it the best district to live in, but the best shops and restaurants of the city are located here.

Hai Ba Trung: HBT gets my vote. You can easily access Hoan Kiem, but are still insulated from the hustle and bustle over there. The growing number of good restaurants and shops in this district can rival Hoan Kiem's in the future. You also have Reunification Park, which is a nice addition. Le Duan street can be a nightmare though.

Ba Dinh: Political center of the city. Also home to the French quarter. Many 2nd and 3rd generation Hanoians live here. Given its central location and safety, expats would also do well to live here.

Dong Da: The district with the highest population density in the city. Certain areas of this district are very dodgy (Lanes off of Kham Thien Street and the area near the train station) and should be avoided. Usually known as the "working class" district. Ba Dinh and Dong Da can be considered "Mid-town"

Cau Giay and Tu Liem: Used to be rice paddies and consequently many people who live here used to be farmers. Many people (and students) who migrated from the countryside to Hanoi also live here. That said, the My Dinh Pham Hung area with a myriad of new condos is attracting many young couples wanting to live on their own.

Thanh Xuan: Very blue collar and also home to many 1st generation Hanoians. This area southeast of the city is usually very dusty owing to new construction and the ring roads. Not a good place to live in.

Hoang Mai: are most heavily affected by the recent flooding. Very high population density thanks to affordable housing prices here. Also very dusty like Thanh Xuan. I hope I never have to live here, though Yen So Park might be nice when it is completed.

Long Bien: Across the Red River. Good if you want to own/operate short-term motels and/or eat snakes.

Ha Dong City, Ha Tay, and the new annexed part of Hanoi: Would probably take at least 10-20 years to develop. Actually Ha Dong City is almost like Hanoi, but it's far away and the thoroughfare of the city is always congested.

Not much to add to what has already been said except that I live close to the train station and have had no problems at all. My flatmates have been living here nearly two years and have never had any problems either so don't discount this area before checking it out as it's easy to get to the Old Quarter from here (10-15 mins walk) plus Hai Ba Trung and Dong Da districts are an easy motorbike trip away.

I think that by checking out NewHanoian before coming over you're already headed in the right direction. Good luck!

Well it's a bit of a blow off answer, but if you are talking about character in where you want to live, I say to get real Hanoi, avoid old quarter, area around Hoan Kiem, try to avoid Tay Ho(West Lake), some good deals but too many expats and way to far to drive, and aviod like the plague Xuan Dieu(White Quater) I like the are around Doi Can and Hoang Hoa Tham, well located and good nice locals, good street food and Bia Hoi, I'd suggest Kim Lien for the same reasons, on Artsy I would suggest are around Tran Phu, arty, old quarter feel but far enough to filter off the Tay Balo, hope this helps and is not too rambly

Oh just a bit extra local local areas have too many roosters, there is nothing good about roosters