Hmmm
I'm unsure as to whether that's aimed at me or not!
Are you referring to the rigmarole of hunting for decent prices or of the rigmarole of US immigration procedures?
If you qualify for entry to the USA under the Visa Waiver Program (and you've not already got valid authorisation to enter) the US authorities recommend applying for an ESTA at least 3 days prior to travel. However it's not a strict rule; most electronic approvals only take a minute or so:
http://london.usembassy.gov/vwp3.html
From researching answers to previous questions on here (from other people who've been seeking trips to New York around Christmas or the New Year), I can tell you that you'll almost certainly have to pay extremely high prices. There appear to be no cheap fares to New York around that time and accommodation is likely to be very pricey.
It's also worth remembering that tyoical New York daytime temperatures, around that time of year, are about 4C, falling to -3C overnight. (However temperatures as high as 20C, or as low as -25C, have been recorded in New York in December and January). Roughly one in three days are wet:
http://www.bbc.co.uk/...lts.shtml?tt=TT001090
Chris