I've always made it a point to treat December 25 as an ordinary day. After all, in the Jewish calender it has no special significant unless Channukah happens to fall out during that time. Yet others in our community seem to want to single it out for special treatment.
Some don't meant to do it in a positive, X-mas affirming sense but rather to take advantage of the civic holiday rules that society has placed on that day. Thus the shul in my town will be davening Shacharis at 8:30 am like on Sundays instead of the usual weekday 7:25 am. As for school, well it's closed for two weeks for winter break. I recall hearing stories about some places in Poland where they would davka make the kids go to cheder in the middle of the break on December 25 but again, that's giving special treatment to the day.
The most incomprehensible to me though is the custom of some Chasidim not to learn Torah on December 25. For them, Nittle Nacht is an opportunity to close their gemaras even though the reasons for this vary. For me, however, this is the worst thing one can do on December 25. Consider:
It is widely accepted that December 25, 0000 was not Yeshu's birthday. When it actually was is far more controversial but it could not have been the 25th because Miriam and Yosef would have been working on the Jewish lunar calendar, thus the Roman date would not have had relevance to remember the day. Further, it is widely know that December 25 is actually a major Roman holiday and that the early Church appropriated it as their annual holiday remember the birth of Yeshu.
Thus for Jews who don't accept that there was anything special about Yeshu, assuming he existed at all (Josephus, for example, never mentions him in his histories of the time), December 25 really is just another day of the week.
I cannot (and only rarely try to do otherwise) speak for others but on December 25 I will get up at my usual weekday time, I will wear my regular work clothes and go and spend the same amount of time in my office I do every other Friday (Heaven knows I'll need the time to clear the paperwork). I will do so to show that tomorrow is not a special day.