Requirements lead to realistic trade-offs which lead to well-informed decisions. This top-down approach is significantly better than the bottoms-up method of touring generally-suitable apartments looking for "the one."
It’s not just an old joke. Location is the most critical decision you will make. You must fit in the place you choose to live. Sure, this is true for real estate anywhere, but it’s even more important in Manhattan where one location, even one right next door to another, can be night-and-day different. Everyone knows this, of course, but not many appreciate what makes locations different, and what differences are important. The people, lifestyle, stores, parks, parking, police, transportation, and lots more are all critical. The avant guard Village, for example, is on another planet when compared to the conservative Upper East side.
But it’s not just “the neighborhood” that’s important. Although it’s possible to make general statements the Upper West Side, Upper East Side, Harlem, Hell’s Kitchen, SOHO, Chinatown, the Financial District, and the Village, it’s the specific street and block that really counts. We fell in love with the Upper West Side (UWS), for example, because we liked the residential feel of the place and the presence of upscale restaurants, high-end stores, transportation, supermarkets…but even on the UWS, every block is different. The culture-rich, touristy Lincoln Center area is very different from the shopping and restaurants found in the Broadway corridor, which is very different from the ritzy, streets adjacent to Central Park, which is very different from the quiet, residential streets near the Hudson river.
You get the idea. To understand this at the level of detail necessary to make a decision about living on a particular block or street, you need to spend time there. Walk around, go to the restaurants, see a movie, sit in the park and people watch, talk to people, take an inventory of what's around, Google the locations and read what people have said, watch for police and fireman, find the bus and subway stops, find out what lines are served and where they go, get information on parking lots and the cost of street parking, take note of the traffic, the noise, the trash, the condition of the streets... The more you know about the location, the more confident you will be in a decision to buy.
Experience the locations you think are right for you first-hand by going there and taking notes. Without notes, unless you are intimately familiar with the place, you will forget what you find, making it difficult to compare on location to another.
I'm sure you have gotten the idea by now--buying an apartment, even a part-time pied-a-terre in manhattan is not for the feint of heart. You can greatly reduce the stress by knowing what decisions you will need to make and by understanding your decision-making options in detail. Most of us who have been around for a while (we're in our 70s) understand that when it comes to real estate, there are no experts. This applies in spades to Manhattan which has its own byzentine rules and conventions. Preparation is the only way to cope and this begins with making a list of decisions.