Restaurants -- 15-20% of the total bill including drinks but before taxes. 20% is the standard for good service. Some restaurants add this on automatically, some don't, so read the bill carefully.
http://www.itipping.com/tip-guide-restau…
Hint: Within NYC the taxes add up to 8.25%, so if you double the tax amount, that's approximately equal to the low end of the range for a reasonable tip.
Bellhop -- $2-3 for each bag carried.
Hotel housekeeping -- Approx. $5/day for good service, more if you left an especially terrible mess.
Bars -- *at least* $1/drink, more if the drinks are expensive (where $1 is 10% or less, you want to add more) or complex to make ($1 is reasonable for popping the cap on a beer bottle for you, while mixing and shaking a cocktail warrants more).
Shopping -- in general, we don't tip for that...but "high end" shopping is not my thing, it may be different for the sex and the city crowd.