Questions about Traveling to Japan?

Question:

I am traveling to Japan in early December and staying through the holidays. I am going to visit my Japanese boyfriend for the first time. He currently lives in Yokahama and is moving to central Tokyo. I was wondering if anyone could give me a few tips on the culture and anything that I should specifically know such as:
1. Fashion styles
-I'm very up to date here in America but would anyone be able to give fashion advice about Tokyo? I am in my early 20's.
2. Any cultural tips that I should keep in mind
3. The weather in December and early January
4. "Do's and don'ts" of the culture
And anything else that is important to know :)
I have been using chopsticks and learning a few phrases in Japanese.
Thank you in advance!! :)

Answer:

There's a web site for street fashion styles.
Tips, don't use your cell on the train. Always remove your shoes when you enter someones home. Don't tip in a restaurant. It'll be cool / cold in Dec / Jan.
Youtube has some cool videos to teach you Japanese.