Snagging a reservation at the restaurant-of-the-moment requires diligence, connections, and the diligent abuse of connections. If you're unconnected/cowardly, but are willing to pay someone who isn't, try Prime Time Tables.
An NYC-based company, PTT's sole purpose is to hook up diners with the toughest reservations in town* -- places foodie scenesters would kill to get into, provided their comical frustration alone could make a maître d's colon explode with rage. Basic membership requires no upfront fee: you just sign up, then pay per usage, selecting from a list of available tables. Your fee varies depending on lead-time -- 2+ days in advance, day before, or, if you're a devil-may-care restaurant whore, same day. You can also size up your options up to 14 days out. Times and party size are preset, but if you need to modify, they'll see what they can do -- whether that means moving you from 8pm to 9pm, or adding a chair to accommodate your ass, lovingly nicknamed "Old Two-Seats"
To screen out bill-skippers/arsonists, membership's by referral only -- but type the Thrillist-only code "gastineau99" in the Referred By box and you're all good. As for how PTT does what it does, it's like hiring someone to unclog a toilet, or "sort out" your neighbor's dog -- as long as you don't have to do anything, don't worry your pretty little head.
*PTT's asked that we not reprint their impressive resto-roster, but also stressed that, on request, they can snag anything, including Per Se.