Hello
こんにちは
kon'nichiwa
Please note that it isn't really that common to greet your friends with this greeting, the follow are more natural
Hiii
やほー
yaho
Hey
ねえ
ne
How are you?
お元気ですか？
おげんきですか
o genki desu ka?
Woah! That looks a bit complicated (assuming youre a beginner), lets break it down...
お (o) shows respect at the start of the sentance. If youre speaking casually, theres no need for it.
元気 (genki) means "well" or "healthy"
です (desu) means "it is" or, in the case, "you are" (i will do another lesson on this verb)
か (ka) is a particle indicating a question
So, all together the sentace literally means "Are you healthy? / are you well?"
Lets see another way you can ask someone how they are...
How are you?
元気？
げんき？
genki?
What's up
調子はどう（ですか？）
ちょうしはどう（ですか？）
choshi wa do (desu ka?)
We can break this one down too...
調子 (choshi) means condition or feeling
は (wa) can be translated as "is" just for simplicity's sake
どう (do) means "how"
So this question literally means "how is your condition" and is a more casual way to ask how someone is