Do you instantly like/dislike something/somene or does it take you awhile to figger it out? Why?

For the most part, yes.  I don't know if it's their body language, how they're dressed, how they smell, my empathic ability, my past life experiences, or a combination thereof.  If something strikes me as the least bit "off" about a person, they're instantly put in my "dislike" category.
Sometimes these "gut feelings" are wrong.   Sometimes my initial dislike is so strong that no matter what a person does, they will never make it to my "like" list (this is especially true with machismo).