Both really because I sometimes plan events and storylines, but more often just play and interpret what happens. I like it best when things happen somewhat simultaneusly. Game gives me ideas for the story and I go with it. For example I had a sim couple not living together but who I wanted to get married but wasn't sure how to proceed. The female sim then called the male sim and asked him to meet at a locale named Wedding Chapel and Barn which is a nightclub in my game. I took that as a hint that they should get engaged and elope on the spot.