Your office holiday party. One of the trickiest sartorial events you may encounter.You basically have 3 choices:1) Be the boring guy who makes no effort and simply wears the same kind of thing he wears to work every other day of the year.2) Be that guy who goes way overboard with a singing santa tie and matching socks.3) Put in just the right amount of effort where actually come off as being effortless with your style.No big shock, my choice for you would be #3. Here’s how to pull off an effortlessly cool holiday party look:1) Start with your everyday office attire, then take that up a notch. So if everyday is:

jeans and t-shirt --> wear chinos and a nicer t-shirt, henley or polo (in this case your office is super casual, so make sure that wherever your party is taking place is not fancy; if it is, opt for one of the options below based on whatever you can find out about the venue. If you're at all unsure, it's always better to be overdressed for something work-related like this.)
chinos and a button-up shirt --> wear dress pants or chinos and a button-up, and add a sportcoat or nice cardigan/v-neck sweater
dress pants and a button-up shirt --> wear dress pants and a button-up, and add a sportcoat
dress pants and a sportcoat --> wear a suit open-collar
a suit and tie --> wear your sharpest, best-fitting suit and a tie that meets one of the criterion below

2) Add 1-2 tasteful, festive touches in the form of a bright color, luxe/wintery fabric, slight sheen or extra panache from the following list:

socks