Here are some examples of how to respond depending on the context:
If the question is "Comment allez-vous?" (How are you?)
* Formal: *Bien, merci. Et vous ?* (Good, thank you. And you?)
* Informal: *Ça va, merci. Et toi ?* (It's going well, thank you. And you?)
If the question is "Comment ça ?" (How is that?)
* *C'est comme ça.* (It's like that.)
* *C'est simple.* (It's simple.)
* *Je ne sais pas.* (I don't know.)
If the question is "Comment s'appelle-t-il ?" (What's his name?)
* *Il s'appelle Jean.* (His name is John.)
* *Je ne sais pas.* (I don't know.)
If the question is "Comment on fait ça ?" (How do you do that?)
* *On fait ça comme ça.* (You do it like this.)
* *C'est facile.* (It's easy.)
To give you a more specific answer, please tell me:
* What is the full question in French?
* What is the context of the question?
For example, is it a question about someone's health, a process, a person's name, or something else?