ya surely "O-genki desu-ka?" means "how r u" in japanese.
but in daily life, japanese never say so cause its too literaly like "how do u do" in English.
so we dont have good way to say "how r u" in practically.
i suggest u to say "ohayou(gozaimasu) / konnichiwa / konbanwa/" = "good mornin / hello / good evenin"
these r easy and acceptable^^