お正月 is oshougatsu, is the New Year celebration. The New Year is also called ganjitsu. On this day, it's a big celebration. Wear your best kimono and have some too-sweet plum wine!
This year begins the Year of the Wood Horse. Horse-born people tend to be straightforward, honest, and lively. They can be high-energy people who don't like the idea of restricted freedom. Naturally, this temperament is said to change somewhat depending on factors such as exact birth hour, element balances, etc. but that's what some people employ fortune-tellers for, isn't it? But no matter what, I think this year will be as good or bad as you make it. Attitude counts for everything. When things go badly, as they inevitably do, how do you approach the situation? With hopelessness, or with a fierce, rampant ambition to make the best of things? This will truly tell your future.
Osechi foods are to be eaten today, a wonderful assortment of konbu (seaweed), ozouni (a type of soup with tofu and herbs), sashimi, and many other foods. As usual, different regions of Japan have different ideas about lucky vs. unlucky foods!
Pay attention to the first dream you have on the 31st or the 1st. Normally, many Japanese do not get to sleep on the night of the 31st, since there is so much celebrating to do. The morning of the 2nd is seen as the end of the first day's dream. There is a superstition that if you dream about one of three things, you will have great luck! Your 初夢 hatsuyume will be fortunate if you dream of hawks, Fujisan, or eggplants. Fujisan, possibly because it is the tallest mountain in Japan, hawks because they are strong, intelligent birds, and eggplants because eggplant is nasu or nasubi 茄子, a homophone for nasu 成す, great achievement. There are a few more additions to this list, but when they were added or why is a source of debate. Have they been there since the original list was founded during the Edo period? Or were they later inventions? Either way, the first three on the list are memorised as Ichi-fuji (first, Fuji), Ni-taka (Second, hawk), San-nasubi (Third, eggplant).
There are many, many kigo related to New Year's Day. Kigo are special seasonal words, and there are entire dictionaries of them to refer to specific events or objects during each season. Most of New Years' kigo begin with Hatsu-, as hatsu- means 'first' in this case. As writing New Year's cards is a huge event even today, knowledge of kigo is especially wonderful when haiku or other poetry is composed for your letters. Of course, not everyone is writing haiku; these letters are often a way of sending well-wishes or letting distant relatives or friends know that you're alive and well. Japan tends to employ many post deliverers to ensure that all the New Years cards get to their recipients on New Year's Day or New Year's Eve. These cards usually include some auspicious symbol or the New Year's animal, and are sometimes hand-drawn by the sender! Each one is surely a treasure, and you should be lucky to receive such a card!
As for me, I worked most of last night, and didn't really do any celebrating. By the time I got home, I only wanted to look at cute animal photos and go to sleep! For the rest of you, 明けましておめでとうございます! Akemashite omedetou gozaimasu! Happy New Year!