Ogenki desu ka?

To ask how someone is you say:

（あなたは） お元気ですか
(Anata wa) ogenki desu ka - How are you? / Are you well / healthy?

The above is the polite way to ask the 'o' before 'genki' is honorific and 'ka' is the question marker. 'Anata wa' means 'You.' 'wa' is simply the subject particle. Has it is clear you are asking the person how they are, you do not need to say 'anata wa' This is normal practice in Japanese.
There are other ways to ask how some one is, examaples being:

元気ですか
Genki desu ka - How are you? / Are you well / healthy?

元気？
Genki? - How are you? / Are you well / healthy?

元気だった？
Genki datta? - How's it going?

大 丈夫ですか
Daijoubu desu ka - Are you OK?

大丈夫？
Daijoubu? - Are you OK?

The above examples should never be said to those in offority or those senior to you, or to strangers. It is best to use the above with friends and family only.