How do i know if a guy likes me?

he dated my bestfriend and we hated each other but then he was in one of my cles and we had to sit next to each other and we became cool with each other. then we became like bestfriends then he dated this other girl i was friends with. but he smoked weed and just smoked and dipped. and im the type of girl who likes dating guys like that and he would lie and do it behind there back. then he broke up with her cause she cheated on him. then he started liking me but he didnt tell me until towards the end of school. and he has told his bro that is dating my bestfriend now that he is in love with me and he stopped smoking nd everything for me and he always wants to make me happy but idk if he will treat me the same as the other gfs or different. and his bro told me that he has smoked but then when i ask him he says he hasnt and his bro wants to get stuff started...help? thanks(: