#1 means you're asking for a comparison or a description. For example, I might respond with "It tastes like apple" or "It tastes sweet." #3 is more like you're asking whether it's good or bad. "It tastes delicious" or "It tastes nasty." #2 is kind of ambiguous. You could respond either of the previous ways. That's why it's not as common to ask "How was the taste?" #4 means something completely different. If someone asked me "How do you taste it?", I would probably respond with "I put my tongue on it..." This is not what you're trying to ask. I would use either #1 or #3, depending on what kind of response you want to ask for.

1,2, and 3 are fine. 4 does not mean the same thing. "How do you taste it?" would elicit an answer such as "with my tongue".