what does dou shiteru mean?

Answer 1

It depends upon the Kanji

1. Why (kinda like "Naze deshou ka?")

2. How do you know (although this would more accurately be written/stated: "Dou shiteiru ? The Tokyo dialect would more readily lend itself to this type of misunderstanding).

3. Absent Kanji (or a written text), I would suggest that you try to discern the meaning from within the context from which it was said.

Akemashite Omedetou! (Happy New Year!)!

Answer 2

It's a Japanese greeting...something like, "How's everything?"