Formal:
* 我很好 (wǒ hěn hǎo): This is the most common and polite way to say "I am fine." It literally means "I am very good."
* 我没事 (wǒ méi shì): This means "I am okay" or "I'm fine" and is often used in response to someone asking if you are alright.
Informal:
* 我挺好的 (wǒ tǐng hǎo de): This means "I'm doing pretty good" and is more casual than "我很好".
* 还可以 (hái kě yǐ): This means "it's okay" or "not bad" and is a more casual way to say "I'm fine".
Adding politeness:
You can add "谢谢 (xiè xie)" meaning "thank you" after any of these phrases to make it more polite, especially if someone is asking how you are.
Examples:
* 你好吗？ (nǐ hǎo ma?) - How are you?
* 我很好，谢谢。 (wǒ hěn hǎo, xiè xie.) - I'm fine, thank you.
* 你感觉怎么样？ (nǐ gǎnjué zěnmeyàng?) - How do you feel?
* 我没事，不用担心。 (wǒ méi shì, bù yòng dānxīn.) - I'm okay, don't worry.
Remember that the best way to say "I am fine" in Chinese depends on the specific situation and the people you are talking to.