kissing him

Im really good friends with my EX and we flirt all the time! and i mean liek big time.. he flirts with me by touching me while watching movies and things. i really want to kiss him... but i dont know if he wants to kiss me.. how do i kiss him with him not freaking out...

just look at him, in the eyes, for a prolonged moment. then slowly move closer so he has a chance to stop you if he doesn't want to but if he doesnt then he clearly does want to kiss you
if for some reason he does stop you just apologise and dont mention it again and act naturally with him to avoid awkwardness