Who's St. Andrew? Even though I know who he is, I thought I'd ask this same question to Wikipedia where I was told that he "is a Christian apostle and the brother of St. Peter." Understatement of the millennium. St. Andrew is pretty awesome, and I don't think he appreciates being put in the shadow of his brother Peter.
More important question. What does one do to celebrate St. Andrew's Day? Based upon my research, the day's festivities traditionally include: flying the flag of Scotland, wearing kilts, eating Scottish shortbread, playing the bagpipes, and watching Sean Connery movies. Okay, I added that last one on my own, though I'm sure it's more than an acceptable way to pay homage to the great nation of Scotland.
Finally, and I believe this to be the easiest way to celebrate St. Andrew's Day and really the least you can do to honor Scotland (whether Scottish or not), drink Scotch whiskey.
Source: Johnnie Walker