Tips on goin to bfs house..im 13?

well im 13 and soon ima be goin to my bfs house...we have been together for over a month now nd hes been to my house a couple times. its not really him im worried about..its his parents!! ive met his dad b4 but not really formally. his stepmom will be therr too and im not shur how i shuld act or dress for this?? plzzz help!! 0_o