Bonenkai season has come. Bonenkai means a "forget-the-year party" directly. Basically it has the meaning to forget the unpleasant memories of the passing year and to prepare oneself to welcome the new year. It is usually held around mid or late December among office colleagues or business acquaintances. So in fact bonenkai tends to be a year-end drinking party free of charge because the companies pay for it.
First of all, we decide on an organizer. At my job, it is the youngest guy every year. Then he picks the best day and confirms the number in attendance. ( but normally it is a sort of duty, Bonenkai at work is a sort of JOB). Then he will choose the party place and make reservations. This is the hardest part because the good places can fill up much earlier and if he chooses a poor place everybody complains :-), but of course the budget is limited.
On the other hand, izakaya tried to set good party menu and get many reservations. For example, Eating and drinking in Tokyo is a n English restaurant search site. And Grouomet Navi has a page "2004 Climax" which is bonenkai special pages.