近しい人：挨拶なし
知り合い：おはよう/こんにちは/こんばんわ
目上の人：おはようございます/こんにちわ/こんばんわ
かな？スカイプはしません。

毎日のようにメールをする仲のよい友人には、
「おはよう」
「こんにちは」
「お疲れさま」
「ハロー」って書きます。
毎日のようにメールをしているなら、（特に携帯の場合は）
挨拶がなくても大丈夫だ（自然だ）と思います。

先輩や、職場の人には、
「お疲れさまです」
と書き始めることが多いです。

Skypeはあまり使うことがないので、
「久しぶり～」
と話し始めることが多いです。

クリス豆腐さん

■携帯電話のメール
：朝「おは。」　[おはようの略]
：昼間や夜「おっす」「元気？」「おつ！」　[お疲れ！の略]
＞ 個人的に「お疲れ様」って、嬉しい反面、何か嫌な言葉に思いますね。
　「我々仲間のために『苦労してくれて』有難う」という意味だから。
　「別に疲れてないよ！」あるいは「疲れるほど活動したのは俺の勝手だから放っておいてくれ！」と思う。けど、何も声掛けられないよりは良いかな・・・

■SKYPE
SKYPEのチャットなども、多分携帯電話のメールと同じかな・・・あまり使ったことないけれど。

携帯のメールでは友人同士は挨拶なしですね。
スカイプのような場合、友人同士ならどの挨拶も使うと思います。
でも、私の周りでは実際に男性の友人同士があったときは「よっ」がよく使われています。

わたしは日本人は他の国の人と比べて
挨拶を重視してないような気もします。
親しい友達にメールするときは　挨拶ははぶくことが多いです。
ひさびさの時は「元気にしてるかい？」というふうな言い方をすることが多いです。

Hi,クリス豆腐。First of all, I think it is ok to send all casual messages you typed to friends. It was interesting to know that you know a kind of slang you cannot easily learn at school. Your friends understand that like " Hey, クリス。Where did you learn these Japanese expressions? " and they maybe think you learned from Japanese comedy shows or dramas or manga. If you use polite expressions to them, they will understand that "Hey Chris, did you read and study Japanse from some textbooks?"

But this is Japanese costom to show respect and politeness to older generation and bosses, so you had be careful to know polite expressions. If you don't know whether it is formal or casual, maybe you can say " ごめんなさい。私の日本語は下手です。でも、これからもっと勉強したいです。私の表現が変だったらごめんなさい。これから、もっと頑張りたいと思います。" to show humbleness, these people won't get offended generally.

Nowadays　email is very convinient tool to send our messages instantly anytime, but I personally think if you would like to keep special friends, maybe you can depend on snail mail to send special message to express mainly positive messages or like " I really miss you. " since you have distance between Japan and Germany. If your friends read snail mails to know special message written by your letters, they maybe read more than several time and keep them because they're impressed and the letter is written by you. If we type, all the letters are exactly same although writing letters comsume more time and energy.But if you are in a hurry to send message to inform some information, it could be better to depend on email.And it is not easy to write letter all the time if you are busy.

I had a such a experience that the Western couple was speaking in fvery ormal Japanse each other. At first, I thought " Why Americans are speaking in very polite Japanse?" But one of them is American and his partner is Brazilian, and their official language is Japanse. Because they speak very formal Japanese although they are a couple, it was interesting to know the lovely couple.

My parents used to write love letters once in a while since they had a long distance for 2 or 3 years. Maybe they used to say " I am very tired and so busy." just like we have a conversation everyday. I don't know the content of the letter. But they eventually got married. My dad is not romantic, so maybe he wrote "I would like to drink beer and I hate to see some couples walking on the street with much happy smile." Maybe my mom felt that he really wanned to see my mom in person.

Good luck and I hope you can keep in touch with your Japanese mates although you have distance.

毎日メールするような相手には挨拶は書かないかもしれませんね。
久しぶりのときは「ひさしぶり!!」て入れます。

Thanks everyone!!!
I think i figured out how to use these greetings (and when to go entirely without greeting) now!