I can’t help re NYC, but some general tips are:
Always, always always look at the fit, NOT the label. A shop might put you at a certain size, but this doesn’t mean you’ll be that same size everywhere you shop. I’ve been measured as a 34C, but I can wear either a 36B, 36C, 34D, or 34Dirty Delete, depending on the make and style, so I always bring a range of sizes into the changing rooms.
A well-fitting bra should fit snuggly on the loosest setting: this is because the elastic gives as you wear them, so if you buy one that fits snuggly on only the tightest setting, it will soon loose elasticity and won’t fit so well.
The strap across the back should sit below your shoulder blades, and sit snuggly without digging in, or creating ‘back fat’.
The straps should be snug and secure, but again not dig in; if you’re bigger busted, go for thick straps. I would also look at bras with a triple hook and eye fastening at the back, rather than the more standard double, as this will give more support.
The cups should sit perfectly across your skin; they should not gape, or be too tight (creating a ‘four boob’ effect). Always bend over, and check the profile from the side.
Style-wise, I tend to go for comfort. My favourite are bras that offer good coverage, as they give more support, and a better shape under clothes IMPO. I would avoid plunge styles as these aren’t as supportive generally speaking. You might also want to consider a long-line bra, as again these offer more support, or a body. Also, buy for your style of dress eg a low back will require something backless or multiway.
Hope This Helps