I think the most casual way is a simple [?]{HLH} (even omitting the ).
How they answer kind of depends on the context, and (probably more so) how close of a relationship you have. For agreement they could use something like , , , , (for the food), (for the outfit), for the movie, etc. For disagreement, things like , , , , …, , and so on.
As you (probably) know, Japanese are very indirect and non-confrontational. So someone is more likely to answer in order to not offend you instead of . Unless it's someone _very_ close to you like your best friends or a sibling.