Konnichiwa, ogenki desu ka. 今日はお元気ですか。

how are you- ogenki desu ka?, and when you answer i'm fine- genki desu. in saying hello..commonly they were saying konnichi wa? saying hello to a friend you haven't seen for a long time..you'll say..konnichi wa! hisashiburi des' ne?... des' ne means-right? in english it will gonna be.. "hello! long time no see.."

How are you is "Ogenki desu ka". The answer to it is "genki desu." Hope this helps.