Travel and pet?

I have a cat and I love her very much. My friends invited me to fly with them to Greece, but I doubt a little. I wouldn't want to leave my cat in a hotel for animals, but I don't know how to prepare for a trip with a pet. What should I do in advance in order to take my cat with me?  I think it would be better for my cat to come with me, but I'm not sure about that.  Maybe someone here has experience traveling with animals and can advise me what will be better for my cat?