This is how you ask for someone's general opinion of something. It's similar to asking "Do you like ___?" but it's a more relaxed-sounding question. You usually ask "How do you like ___?" when you're first finding out what a person thinks about a new situation:

How do you like your new house?

How do you like working with Randall?

So how do you like California?

A good answer to "How do you like ___?" is something like:

It's great!

or

It's been pretty tough, actually.

You might mix "How do you like ___?" with "What is ___ like?" but they're different. Ask "How do you like ___?" to get someone's review or rating. Ask "What is ___ like?" to hear a description.