Хорошо (Horosho)
This is a general expression meaning "good" or "well" and is used in many contexts, including when responding to "How are you?"
Here are some other options, depending on the situation:
* У меня все хорошо (U menya vse khorosho): "Everything is good with me."
* Нормально (Normal'no): "Normal" or "okay."
* Отлично (Otlichno): "Excellent."
* Хорошо, спасибо (Horosho, spasibo): "Good, thank you."
The best choice will depend on the specific context of your conversation.